Available for both mongod and mongos.

Specifies the list of authentication mechanisms the server accepts. Set this to one or more of the following values. If you specify multiple values, use a comma-separated list and no spaces. For descriptions of the authentication mechanisms, see Authentication.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to specify both PLAIN and SCRAM-SHA-256 as the authentication mechanisms, use the following command:

  mongod --setParameter authenticationMechanisms=PLAIN,SCRAM-SHA-256 --auth

In previous versions, AWS IAM authentication retried only when the server returned an HTTP 500 error.

Available for both mongod and mongos.

Type: integer

Default: 2

For MongoDB deployments using AWS IAM credentials (https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html) or AWS IAM environment variables (https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-envvars.html#envvars-list).

Maximum number of AWS IAM authentication retries after a connection failure.

The following example sets awsSTSRetryCount to 15 retries:

  mongod --setParameter awsSTSRetryCount=15

Alternatively, the following examples uses the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, awsSTSRetryCount: 15 } )

Available for both mongod and mongos.

Set the clusterAuthMode to either sendX509 or x509. Useful during rolling upgrade to use x509 for membership authentication to minimize downtime.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients .

This parameter is only available at runtime. To set the parameter, use the setParameter command.

  db.adminCommand( { setParameter: 1, clusterAuthMode: "sendX509" } )

Available for both mongod and mongos.

Default: true

Specify 0 or false to disable localhost authentication bypass. Enabled by default.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

See Localhost Exception for more information.

Available for both mongod and mongos.

Set to false to disable the O/OU/DC check when clusterAuthMode is keyFile in your configuration file. This allows clients possessing member certificates to authenticate as users stored in the $external database. The server won't start if clusterAuthMode isn't keyFile in your configuration file.

To set the enforceUserClusterSeparation parameter to false, run the following command during startup:

  mongod --setParameter enforceUserClusterSeparation=false

If you set the enforceUserClusterSeparation parameter to false, the server doesn't distinguish between client certificates, which applications use to authenticate, and intra-cluster certificates, which have privileged access. This has no effect if your clusterAuthMode is keyFile. However, if your clusterAuthMode is x509, user certificates that use the allowed scheme are conflated with cluster certificates and granted privileged access.

Your existing certificates are granted internal privileges if you do the following:

You must not upgrade from keyFile to x509 without validating that you've removed users with elevated privileges that the enforceUserClusterSeparation flag allowed you to create.

Default: 7776000 seconds (90 days)

Specifies the number of seconds for which an HMAC signing key (https://en.wikipedia.org/wiki/Hash-based_message_authentication_code) is valid before rotating to the next one. This parameter is intended primarily to facilitate authentication testing.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Default: false

Enables the performance of concurrent LDAP operations.

Only if you are certain that your instance of libldap is safe to use in this mode, enable this flag. You may experience crashes of the MongoDB process if the libldap version you are using is not thread safe.

You must use ldapForceMultiThreadMode to use LDAP connection pool. To enable LDAP connection pool, set ldapForceMultiThreadMode and ldapUseConnectionPool to true.

If you have any concerns regarding your MongoDB version, OS version or libldap version, please contact MongoDB Support.

Available for both mongod and mongos.

Type: string

The password used to bind to an LDAP server. You must use ldapQueryUser with this parameter.

If not set, mongod or mongos does not attempt to bind to the LDAP server.

Available for both mongod and mongos.

Type: string

The user that binds to an LDAP server. You must use ldapQueryPassword with this parameter.

If not set, mongod or mongos does not attempt to bind to the LDAP server.

Available for both mongod and mongos.

Type: integer

Default: 0

For MongoDB deployments using LDAP Authorization.

Number of operation retries by the server LDAP manager after a network error.

For example, the following sets ldapRetryCount to 3 seconds:

  mongod --ldapRetryCount=3

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, ldapRetryCount: 3 } )

Available for mongod only.

Starting in MongoDB 5.2, the update interval for cached user information retrieved from an LDAP server depends on ldapShouldRefreshUserCacheEntries:

For use with MongoDB deployments using LDAP Authorization.

The interval (in seconds) that the mongod instance waits between external user cache flushes. After MongoDB flushes the external user cache, MongoDB reacquires authorization data from the LDAP server the next time an LDAP-authorized user issues an operation.

Increasing the value specified increases the amount of time MongoDB and the LDAP server can be out of sync, but reduces the load on the LDAP server. Conversely, decreasing the value specified decreases the time MongoDB and the LDAP server can be out of sync while increasing the load on the LDAP server.

Defaults to 30 seconds.

Available for mongod only.

Type: integer

Default: 30 seconds

Starting in MongoDB 5.2, the update interval for cached user information retrieved from an LDAP server depends on ldapShouldRefreshUserCacheEntries:

For MongoDB deployments using LDAP Authorization.

The interval in seconds that mongod waits before refreshing the cached user information from the LDAP server.

The maximum interval is 86,400 seconds (24 hours).

For example, the following sets ldapUserCacheRefreshInterval to 4000 seconds:

  mongod --setParameter ldapUserCacheRefreshInterval=4000

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, ldapUserCacheRefreshInterval: 4000 } )

Available for mongod only.

Type: integer

Default: 90 seconds

For MongoDB deployments using LDAP Authorization.

The interval in seconds that mongod retains the cached LDAP user information after the last cache refresh.

If more than ldapUserCacheStalenessInterval seconds elapse without a successful refresh of the user information from the LDAP server, then mongod:

The maximum interval is 86,400 seconds (24 hours).

For example, the following sets ldapUserCacheStalenessInterval to 4000 seconds:

  mongod --setParameter ldapUserCacheStalenessInterval=4000

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, ldapUserCacheStalenessInterval: 4000 } )

Specifies whether MongoDB should use connection pooling when connecting to the LDAP server for authentication/authorization.

MongoDB uses the following default values:

You can only set ldapUseConnectionPool during start-up, and cannot change this setting with the setParameter database command.

Default: true

A boolean that determines whether the LDAP connection pool (see ldapUseConnectionPool) should use latency of the LDAP servers to determine the connection order (from lowest latency to highest).

You can only set ldapConnectionPoolUseLatencyForHostPriority during start-up, and cannot change this setting during run time with the setParameter database command.

Default: 1

The minimum number of connections to keep open to each LDAP server.

You can only set ldapConnectionPoolMinimumConnectionsPerHost during start-up, and cannot change this setting during run time with the setParameter database command.

Changed starting in MongoDB versions 5.0.9 and 6.0.0 Changed default value to 2147483647. In previous versions, the default is unset.

Default: 2147483647

The maximum number of connections to keep open to each LDAP server.

You can only set ldapConnectionPoolMaximumConnectionsPerHost during start-up, and cannot change this setting during run time with the setParameter database command.

Changed starting in MongoDB versions 5.0.9 and 6.0.0 Changed default value to 2. In previous versions, the default is unset.

Default: 2

The maximum number of in-progress connect operations to each LDAP server.

You can only set ldapConnectionPoolMaximumConnectionsInProgressPerHost during start-up, and cannot change this setting with the setParameter database command.

Default: 60000

The number of milliseconds in-between health checks of the pooled LDAP connections.

You can only set ldapConnectionPoolHostRefreshIntervalMillis during start-up, and cannot change this setting with the setParameter database command.

Default: 300

The maximum number of seconds that the pooled connections to an LDAP server can remain idle before being closed.

You can only set ldapConnectionPoolIdleHostTimeoutSecs during start-up, and cannot change this setting with the setParameter database command.

Available for mongod only.

Type: boolean

Default: true

For MongoDB deployments using LDAP Authorization.

Starting in MongoDB 5.2, the update interval for cached user information retrieved from an LDAP server depends on ldapShouldRefreshUserCacheEntries:

You can only set ldapShouldRefreshUserCacheEntries during startup in the configuration file or with the --setParameter option on the command line. For example, the following disables ldapShouldRefreshUserCacheEntries:

  mongod --setParameter ldapShouldRefreshUserCacheEntries=false

Default: 200

The maximum memory usage limit in megabytes for the validate command. If the limit is exceeded, validate returns as many results as possible and warns that not all corruption might be reported because of the limit.

This parameter is available both at runtime and at startup:

Use this parameter to specify identity provider (IDP) configurations when using OpenID Connect Authentication.

oidcIdentityProviders accepts an array of zero or more identity provider (IDP) configurations. An empty array (default) indicates no OpenID Connect support is enabled. When more than one IDP is defined, oidcIdentityProviders uses the matchPattern field to select an IDP. Array order determines the priority and the first IDP is always selected.

•

•

•

•

•

•

•

•

•

•

•

•

•

Available on Linux and macOS.

Default: true

The flag that enables or disables OCSP.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following disables OCSP:

  mongod --setParameter ocspEnabled=false ...

Starting in MongoDB 6.0, if ocspEnabled is set to true during initial sync, all nodes must be able to reach the OCSP responder.

If a member fails in the STARTUP2 state, set tlsOCSPVerifyTimeoutSecs to a value that is less than 5.

Available on Linux.

The number of seconds to wait before refreshing the stapled OCSP status response. Specify a number greater than or equal to 1.

You can only set ocspValidationRefreshPeriodSecs during startup in the configuration file or with the --setParameter option on the command line. For example, the following sets the parameter to 3600 seconds:

  mongod --setParameter ocspValidationRefreshPeriodSecs=3600 ...

Starting in MongoDB 5.0, the rotateCertificates command and db.rotateCertificates() method will also refresh any stapled OCSP responses.

Available on Linux only

With the use of native TLS/SSL libraries, the parameter opensslCipherConfig is supported for Linux/BSD and no longer supported in Windows and macOS.

Specify the cipher string for OpenSSL when using TLS/SSL encryption. For a list of cipher strings, see https://www.openssl.org/docs/man1.1.1/man1/ciphers.html (https://www.openssl.org/docs/man1.1.1/man1/ciphers.html). Multiple cipher strings can be provided as a colon-separated list.

This parameter is only for use with TLS 1.2 or earlier. To specify cipher suites for use with TLS 1.3, use the opensslCipherSuiteConfig parameter.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

The use of TLS options is preferred over SSL options. The TLS options have the same functionality as the SSL options. The following example configures a mongod with a opensslCipherConfig cipher string of 'HIGH:!EXPORT:!aNULL@STRENGTH':

  mongod --setParameter opensslCipherConfig='HIGH:!EXPORT:!aNULL@STRENGTH' --tlsMode requireTLS --tlsCertificateKeyFile Certs/server.pem

Available on Linux only

Specify the list of supported cipher suites OpenSSL should permit when using TLS 1.3 encryption.

For a list of cipher suites for use with TLS 1.3, see https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_cipher_list.html (https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_cipher_list.html). Multiple cipher suites can be provided as a colon-separated list.

This parameter is only for use with TLS 1.3. To specify cipher strings for use with TLS 1.2 or earlier, use the opensslCipherConfig parameter.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following configures a mongod with a opensslCipherSuiteConfig cipher suite of 'TLS_AES_256_GCM_SHA384' for use with TLS 1.3:

  mongod --setParameter opensslCipherSuiteConfig='TLS_AES_256_GCM_SHA384' --tlsMode requireTLS --tlsCertificateKeyFile Certs/server.pem

Available on Linux only

Specify the path to the PEM file that contains the OpenSSL Diffie-Hellman parameters when using TLS 1.2 or previous. Specifying the OpenSSL Diffie-Hellman parameters enables support for Ephemeral Diffie-Hellman (DHE) cipher suites during TLS/SSL encryption.

This parameter is not supported for use with TLS 1.3.

Ephemeral Diffie-Hellman (DHE) cipher suites (and Ephemeral Elliptic Curve Diffie-Hellman (ECDHE) cipher suites) provide Forward Secrecy. Forward Secrecy cipher suites create an ephemeral session key that is protected by the server's private key but never transmitted. This ensures that even if a server's private key is compromised, you cannot decrypt past sessions with the compromised key.

If opensslDiffieHellmanParameters is unset but ECDHE is enabled, MongoDB enables DHE using the ffdhe3072 Diffie-Hellman parameter, as defined in RFC-7919#appendix-A.2 (https://tools.ietf.org/html/7919#appendix-A.2). The ffdhe3072 is a strong parameter (specifically, size is greater than 1024). Strong parameters are not supported with Java 6 and 7 unless extended support has been purchased from Oracle.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

If for performance reasons, you need to disable support for DHE cipher suites, use the opensslCipherConfig parameter:

  mongod --setParameter opensslCipherConfig='HIGH:!EXPORT:!aNULL:!DHE:!kDHE@STRENGTH' ...

Available for both mongod and mongos.

Specify the path to the Unix Domain Socket of the saslauthd instance to use for proxy authentication.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for both mongod and mongos.

saslHostName overrides MongoDB's default hostname detection for the purpose of configuring SASL and Kerberos authentication.

saslHostName does not affect the hostname of the mongod or mongos instance for any purpose beyond the configuration of SASL and Kerberos.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

saslHostName supports Kerberos authentication and is only included in MongoDB Enterprise. For more information, see the following:

Available for both mongod and mongos.

Allows users to override the default Kerberos service name component of the Kerberos principal name, on a per-instance basis. If unspecified, the default value is mongodb.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

saslServiceName is only available in MongoDB Enterprise.

Ensure that your driver supports alternate service names.

Available for both mongod and mongos.

Default: 10000

Changes the number of hashing iterations used for all new SCRAM-SHA-1 passwords. More iterations increase the amount of time required for clients to authenticate to MongoDB, but makes passwords less susceptible to brute-force attempts. The default value is ideal for most common use cases and requirements.

If you modify this value, it does not change the iteration count for existing passwords. The scramIterationCount value must be 5000 or greater.

This parameter is available both at runtime and at startup:

For example, the following sets the scramIterationCount to 12000.

  mongod --setParameter scramIterationCount=12000

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, scramIterationCount: 12000 } )

Available for both mongod and mongos.

Default: 15000

Changes the number of hashing iterations used for all new SCRAM-SHA-256 passwords. More iterations increase the amount of time required for clients to authenticate to MongoDB, but makes passwords less susceptible to brute-force attempts. The default value is ideal for most common use cases and requirements.

If you modify this value, it does not change iteration count for existing passwords. The scramSHA256IterationCount value must be 5000 or greater.

This parameter is available both at runtime and at startup:

For example, the following sets the scramSHA256IterationCount to 20000.

  mongod --setParameter scramSHA256IterationCount=20000

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, scramSHA256IterationCount: 20000 } )

Available for both mongod and mongos.

Set the net.ssl.mode to either preferSSL or requireSSL. Useful during rolling upgrade to TLS/SSL to minimize downtime.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients .

This parameter is only available at runtime. To set the parameter, use the setParameter command.

  db.adminCommand( { setParameter: 1, sslMode: "preferSSL" } )

tlsMode

Available for both mongod and mongos.

Set to either:

The tlsMode parameter is useful during rolling upgrade to TLS/SSL to minimize downtime.

This parameter is only available at runtime. To set the parameter, use the setParameter command.

  db.adminCommand( { setParameter: 1, tlsMode: "preferTLS" } )

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients .

sslMode

Overrides the clusterAuthX509 configuration options.

  setParameter:


     tlsClusterAuthX509Override: { attributes: O=MongoDB, OU=MongoDB Server }

The parameter supports attributes and extensionValue overrides.

When the server authenticates connections from members, it analyzes the X.509 certificate to determine whether it belongs to a cluster member. If the server uses the attributes setting or the attributes field on the tlsClusterAuthX509Override parameter, it checks the Distinguished Name (DN) values of the certificate. If the extensionValue setting or the extensionValue field of the tlsClusterAuthX509Override parameter is set, it checks the extension values of the certificate. If it finds a match, it authorizes the connection as a peer.

Use this parameter to rotate certificates when the new certificates have different attributes or extension values.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for Linux.

The maximum number of seconds the mongod / mongos instance should wait to receive the OCSP status response for its certificates.

Specify an integer greater than or equal to (>=) 1. If unset, tlsOCSPStaplingTimeoutSecs uses the tlsOCSPVerifyTimeoutSecs value.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following sets the tlsOCSPStaplingTimeoutSecs to 20 seconds:

  mongod --setParameter tlsOCSPStaplingTimeoutSecs=20 ...

Available for Linux and Windows.

Default: 5

The maximum number of seconds that the mongod / mongos should wait for the OCSP response when verifying server certificates.

Specify an integer greater than or equal to (>=) 1.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following sets the tlsOCSPVerifyTimeoutSecs to 20 seconds:

  mongod --setParameter tlsOCSPVerifyTimeoutSecs=20 ...

Available for mongod only.

Type: boolean

Default: false

Specifies whether MongoDB loads TLS certificates that are already available to the operating system's certificate authority.

When starting a mongod instance with TLS/SSL enabled, you must specify a value for the --tlsCAFile flag, the net.tls.CAFile configuration option, or the tlsUseSystemCA parameter.

--tlsCAFile, tls.CAFile, and tlsUseSystemCA are all mutually exclusive.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set tlsUseSystemCA to true:

  mongod --setParameter tlsUseSystemCA=true

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients .

Available for both mongod and mongos.

Default: false

A TLS certificate is set for a mongod or mongos either by the --tlsClusterFile option or by the --tlsCertificateKeyFile option when --tlsClusterFile is not set. If the TLS certificate is set, by default, the instance sends the certificate when initiating intra-cluster communications with other mongod or mongos instances in the deployment. Set tlsWithholdClientCertificate to 1 or true to direct the instance to withhold sending its TLS certificate during these communications. Use this option with --tlsAllowConnectionsWithoutCertificates (to allow inbound connections without certificates) on all members of the deployment. tlsWithholdClientCertificate is mutually exclusive with --clusterAuthMode x509.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for both mongod and mongos.

An alternative Distinguished Name (DN) that the instance can also use to identify members of the deployment.

For a MongoDB deployment that uses x.509 certificates for clusterAuthMode, deployment members identify each other using x.509 certificates ( net.tls.clusterFile, if specified, and net.tls.certificateKeyFile) during intra-cluster communications. For members of the same deployment, the DN from their certificates must have the same Organization attributes (O's), the Organizational Unit attributes (OU's), and the Domain Components (DC's).

If tlsX509ClusterAuthDNOverride is set for a member, the member can also use the override value when comparing the DN components (O's, OU's, and DC's) of the presented certificates. That is the member checks the presented certificates against its net.tls.clusterFile/net.tls.certificateKeyFile. If the DN does not match, the member checks the presented certificate against the tlsX509ClusterAuthDNOverride value.

If set, you must set this parameter on all members of the deployment.

This parameter is available both at runtime and at startup:

You can use this parameter for a rolling update of certificates to new certificates that contain a new DN value. See Rolling Update of x.509 Cluster Certificates that Contain New DN.

For more information about membership certificate requirements, see Member Certificate Requirements for details.

Available for both mongod and mongos.

Default : 30

mongod / mongos logs a warning on connection if the presented x.509 certificate expires within 30 days of the mongod/mongos system clock. Use the tlsX509ExpirationWarningThresholdDays parameter to control the certificate expiration warning threshold:

This parameter has a minimum value of 0.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

See x.509 Certificates Nearing Expiry Trigger Warnings for more information on x.509 expiration warnings.

For more information on x.509 certificate validity, see RFC 5280 4.1.2.5 (https://tools.ietf.org/html/rfc5280#section-4.1.2.5).

Available for mongos only.

Default: 30

On a mongos instance, specifies the interval (in seconds) at which the mongos instance checks to determine whether the in-memory cache of user objects has stale data, and if so, clears the cache. If there are no changes to user objects, mongos will not clear the cache.

This parameter has a minimum value of 1 second and a maximum value of 86400 seconds (24 hours).

This parameter is available both at runtime and at startup:

Available for both mongod and mongos.

Default: 0

Available in MongoDB Enterprise only.

The number of milliseconds to wait before informing clients that their authentication attempt has failed. This parameter may be in the range 0 to 5000, inclusive.

Setting this parameter makes brute-force login attacks on a database more time-consuming. However, clients waiting for a response from the MongoDB server still consume server resources, and this may adversely impact benign login attempts if the server is denying access to many other clients simultaneously.

Available for both mongod and mongos.

Default: true

A boolean flag that allows or disallows the retrieval of authorization roles from client x.509 certificates.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongod only.

Default: True

Starting in MongoDB 6.0, pipeline stages that require more than 100 megabytes of memory to execute write temporary files to disk by default. These temporary files last for the duration of the pipeline execution and can influence storage space on your instance. In earlier versions of MongoDB, you must pass { allowDiskUse: true } to individual find and aggregate commands to enable this behavior.

Individual find and aggregate commands can override the allowDiskUseByDefault parameter by either:

This parameter is available both at runtime and at startup:

  mongod --setParameter allowDiskUseByDefault=false

allowDiskUseByDefault only works on mongod not mongos. mongos never writes temporary files to disk. Use the setParameter command in a mongosh session that is connected to a running mongod to change the value of the parameter while the server is running:

  db.adminCommand(


    {


        setParameter: 1,


        allowDiskUseByDefault: false


    }


  )

Available for both mongod and mongos.

Adds more verbose tracing for curl on Linux and macOS. Has no affect on Windows.

By default, the parameter is unset.

This parameter is available both at runtime and at startup:

  mongos --setParameter httpVerboseLogging=true

Available for both mongod and mongos.

Default: 100

Sets the time limit in milliseconds to log the establishment of slow server connections.

If a connection takes longer to establish than the slowConnectionThresholdMillis parameter, an event is added to the log with the message msg field set to "Slow connection establishment".

This parameter is available both at runtime and at startup:

The following example sets slowConnectionThresholdMillis to 250 milliseconds.

  mongod --setParameter slowConnectionThresholdMillis=250

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, slowConnectionThresholdMillis: 250 } )

Available for both mongod and mongos.

Default: 200

Sets the maximum size of the legacy connection pools for outgoing connections to other mongod instances in the global connection pool. The size of a pool does not prevent the creation of additional connections, but does prevent a connection pool from retaining connections in excess of the value of connPoolMaxConnsPerHost.

The parameter is separate from the connections in TaskExecutor pools. See ShardingTaskExecutorPoolMaxSize.

Only adjust this setting if your driver does not pool connections and you're using authentication in the context of a sharded cluster.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter connPoolMaxConnsPerHost=250

Available for both mongod and mongos.

Sets the maximum number of in-use connections at any given time for for outgoing connections to other mongod instances in the legacy global connection pool.

By default, the parameter is unset.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter connPoolMaxInUseConnsPerHost=100

connPoolMaxConnsPerHost

Available for both mongod and mongos.

Sets the time limit that connection in the legacy global connection pool can remain idle before being closed.

By default, the parameter is unset.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongos --setParameter globalConnPoolIdleTimeoutMinutes=10

Available for both mongod and mongos.

Default: 600000 (10 minutes)

Sets the expiration threshold in milliseconds for idle cursors before MongoDB removes them; specifically, MongoDB removes cursors that have been idle for the specified cursorTimeoutMillis.

This parameter is available both at runtime and at startup:

For example, the following sets the cursorTimeoutMillis to 300000 milliseconds (5 minutes).

  mongod --setParameter cursorTimeoutMillis=300000

Or, if using the setParameter command within mongosh:

  db.adminCommand( { setParameter: 1, cursorTimeoutMillis: 300000 } )

Setting cursorTimeoutMillis to less than or equal to 0 results in all cursors being immediately eligible for timeout. Generally, the timeout value should be greater than the average amount of time for a query to return results. Use tools like the cursor.explain() cursor modifier to analyze the average query time and select an appropriate timeout period.

MongoDB cleans up orphaned cursors linked to sessions as part of session management. This means that orphaned cursors with session ids do not use cursorTimeoutMillis to control the timeout.

For operations that return a cursor and have an idle period longer than localLogicalSessionTimeoutMinutes, use Mongo.startSession() to perform the operation within an explicit session. To refresh the session, run the refreshSessions command. For details, see Refresh a Cursor with refreshSessions.

Available for mongod only.

Type: integer

Default: 3

Sets the maximum number of concurrent index builds allowed on the primary. This is a global limit that applies across all collections.

Increasing the value of maxNumActiveUserIndexBuilds allows additional concurrent index builds at the cost of increased pressure on the WiredTiger cache.

System indexes are not limited to maxNumActiveUserIndexBuilds, however a system index build counts against the limit for user index builds.

After the server reaches maxNumActiveUserIndexBuilds, it blocks additional user index builds until the number of concurrent index builds drops below the maxNumActiveUserIndexBuilds limit. If an index build is blocked, the server logs this message:

  Too many index builds running simultaneously, waiting until the


  number of active index builds is below the threshold.

This parameter is available both at runtime and at startup:

The following command sets a limit of 4 concurrent index builds:

  db.adminCommand( { setParameter: 1, maxNumActiveUserIndexBuilds: 4 } )

See also:

Available for mongod only.

Specify whether all queries must use indexes. If 1, MongoDB will not execute queries that require a collection scan and will return an error.

Consider the following example which sets notablescan to 1 or true:

  db.adminCommand( { setParameter: 1, notablescan: 1 } )

Setting notablescan to 1 can be useful for testing application queries, for example, to identify queries that scan an entire collection and cannot use an index.

To detect unindexed queries without notablescan, consider reading the Analyze Query Performance and Optimize Query Performance sections and using the logLevel parameter, mongostat and profiling.

Don't run production mongod instances with notablescan because preventing collection scans can potentially affect queries in all databases, including administrative queries.

This parameter is available both at runtime and at startup:

notablescan does not allow unbounded queries that use a clustered index because the queries require a full collection scan. For more information, see Collection Scans.

Available for mongod only.

Default: true

To support TTL Indexes, mongod instances have a background thread that is responsible for deleting documents from collections with TTL indexes.

This parameter is available both at runtime and at startup:

To disable this worker thread for a mongod, set ttlMonitorEnabled to false, as in the following operations:

  db.adminCommand( { setParameter: 1, ttlMonitorEnabled: false } )

Alternately, you may disable the thread at startup time by starting the mongod instance with the following option:

  mongod --setParameter ttlMonitorEnabled=false

Do not run production mongod instances with ttlMonitorEnabled disabled, except under guidance from MongoDB support. Preventing TTL document removal can negatively impact MongoDB internal system operations that depend on TTL Indexes.

Available for both mongod and mongos.

Default: true

Enables support for accepting inbound TCP Fast Open (TFO) connections to the mongod/mongos from a client. TFO requires both the client and mongod/mongos host machine support and enable TFO:

Windows

macOS

Linux

This parameter has no effect if the host operating system does not support or is not configured to support TFO connections.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

See Support for TCP Fast Open for more information on MongoDB TFO support.

RFC7413 (https://tools.ietf.org/html/rfc7413).

Available for both mongod and mongos.

Default: true

Linux Operating System Only

Enables support for outbound TCP Fast Open (TFO) connections from the mongod/mongos to a client. TFO requires both the client and the mongod/mongos host machine support and enable TFO.

Linux operating systems running Linux Kernel 4.11 or later can support outbound TFO.

Set the value of /proc/sys/net/ipv4/tcp_fastopen to enable outbound TFO connections:

This parameter has no effect if the host operating system does not support or is not configured to support TFO connections.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

See Support for TCP Fast Open for more information on MongoDB TFO support.

RFC7413 (https://tools.ietf.org/html/rfc7413).

Available for both mongod and mongos.

Default: 1024

As part of establishing a TCP Fast Open (TFO) connection, the client submits a valid TFO cookie to the mongod/mongos before completion of the standard TCP 3-way handshake. The mongod/mongos keeps a queue of all such pending TFO connections.

The tcpFastOpenQueueSize parameter sets the size of the queue of pending TFO connections. While the queue is full, the mongod/mongos falls back to the normal three-way handshake for incoming client requests and ignores the presence of TFO cookies. Once the queue size falls back below the limit, the mongod/mongos begins accepting new TFO cookies.

This parameter has no effect on host operating systems that do not support or are not configured for TFO connections. See Support for TCP Fast Open for more information on MongoDB TFO support.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongod only.

The MongoDB JavaScript engine uses SpiderMonkey, which implements Just-in-Time (JIT) compilation for improved performance when running scripts.

This parameter is available both at runtime and at startup:

To enable the JIT, set disableJavaScriptJIT to false, as in the following example:

  db.adminCommand( { setParameter: 1, disableJavaScriptJIT: false } )

$where will reuse existing JavaScript interpreter contexts, so changes to disableJavaScriptJIT may not take effect immediately for these operations.

Alternately, you may enable the JIT at startup time by starting the mongod instance with the following option:

  mongod --setParameter disableJavaScriptJIT=false

Available for mongod only.

Default: 500 MB

Sets the minimum available disk space in megabytes required for index builds.

Must be greater than or equal to 0 MB, and less than or equal to 8 TB. 0 disables the minimum disk space requirement.

A new index build cannot be started and a current index build is cancelled if the available disk space is below indexBuildMinAvailableDiskSpaceMB.

If you increase indexBuildMinAvailableDiskSpaceMB, ensure your server has enough available disk space. Also, if you set indexBuildMinAvailableDiskSpaceMB too high, you might needlessly prevent index builds when there is enough available disk space and indexBuildMinAvailableDiskSpaceMB could be set lower.

This parameter is available both at runtime and at startup:

The following example sets indexBuildMinAvailableDiskSpaceMB to 650 MB:

  db.adminCommand( { setParameter: 1, indexBuildMinAvailableDiskSpaceMB: 650 } )

You can also set indexBuildMinAvailableDiskSpaceMB at startup. For example:

  mongod --setParameter indexBuildMinAvailableDiskSpaceMB=650

Default: 100000

Limits the maximum number of keys generated for a document to prevent out of memory errors. It is possible to raise the limit, but if an operation requires more keys than the indexMaxNumGeneratedKeysPerDocument parameter specifies, the operation will fail.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Default: 200

Limits the amount of memory that simultaneous index builds on one collection may consume for the duration of the builds. The specified amount of memory is shared between all indexes built using a single createIndexes command or its shell helper db.collection.createIndexes().

This parameter is available both at runtime and at startup:

The memory consumed by an index build is separate from the WiredTiger cache memory (see cacheSizeGB).

maxIndexBuildMemoryUsageMegabytes sets a limit on how much memory the index build uses at once. This can impact performance when the index build process generates and sorts keys for the index. Increasing the memory limit improves sorting performance during an index build.

Index builds may be initiated either by a user command such as createIndexes or by an administrative process such as an initial sync. Both are subject to the limit set by maxIndexBuildMemoryUsageMegabytes.

An initial sync populates only one collection at a time and has no risk of exceeding the memory limit. However, it is possible for a user to start index builds on multiple collections in multiple databases simultaneously and potentially consume an amount of memory greater than the limit set by maxIndexBuildMemoryUsageMegabytes.

To minimize the impact of building an index on replica sets and sharded clusters with replica set shards, use a rolling index build procedure as described on Rolling Index Builds on Replica Sets.

Changing maxIndexBuildMemoryUsageMegabytes does not affect an in progress index build if it has already started a collection scan. However, a forced replica set reconfiguration restarts the collection scan and uses the most current maxIndexBuildMemoryUsageMegabytes provided.

Default: false

A boolean flag that determines whether the db.serverStatus() method and serverStatus command return opWriteConcernCounters information.

  mongod --setParameter reportOpWriteConcernCountersInServerStatus=true

Available for mongod only.

Type: integer

Default: -1 (disabled)

Determines how frequent the Storage Node Watchdog checks the status of the monitored filesystems:

Valid values for watchdogPeriodSeconds are:

To enable Storage Node Watchdog, watchdogPeriodSeconds must be set during startup.

  mongod --setParameter watchdogPeriodSeconds=60

You can only enable the Storage Node Watchdog at startup. However, once enabled, you can pause the Storage Node Watchdog or change the watchdogPeriodSeconds during run time.

Once enabled,

It is an error to set watchdogPeriodSeconds at run time if the Storage Node Watchdog was not enabled at startup time.

To release memory back to the operating system, consider using tcmallocEnableBackgroundThread instead.

Type: integer (0 or 1 only)

Default: 0

If you enable tcmallocAggressiveMemoryDecommit, MongoDB:

A value of 1 enables tcmallocAggressiveMemoryDecommit; 0 disables this parameter.

This parameter is available both at runtime and at startup:

If you enable this parameter, the system will require new memory allocations for use. Consider enabling tcmallocAggressiveMemoryDecommit only on memory-constrained systems and after pursuing other memory and performance options.

Type: boolean

Default: true

If set to true, tcmallocEnableBackgroundThread creates a background thread that periodically releases memory back to the operating system. The value of tcmallocReleaseRate determines the rate, in bytes per second, at which the background thread releases memory.

If tcmallocEnableBackgroundThread is true and tcmallocReleaseRate is 0, MongoDB still releases memory.

For improved memory usage, we recommend using the default value of true. To learn more about improvements to performance and memory management, see Upgraded TCMalloc.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

The following operation sets tcmallocEnableBackgroundThread to false:

  mongod --setParameter "tcmallocEnableBackgroundThread=false"

Default: 0

Specifies the tcmalloc release rate (https://github.com/google/tcmalloc/blob/master/docs/tuning.md) in bytes per second. Release rate refers to the rate at which MongoDB releases unused memory to the system. If tcmallocReleaseRate is set to 0 MongoDB doesn't release memory back to the system. Increase this value to return memory faster; decrease it to return memory slower.

If tcmallocEnableBackgroundThread is true and tcmallocReleaseRate is 0, MongoDB still releases memory.

Starting in MongoDB 8.0, the default value of tcmallocReleaseRate is reduced to 0 due to a tcmalloc upgrade that prioritizes CPU performance over memory release. Earlier versions of MongoDB used an older version of tcmalloc that set the default tcmallocReleaseRate to 1 to balance memory release and performance.

This parameter is available both at runtime and at startup:

To modify the release rate during run time, you can use the setParameter command; for example:

  db.adminCommand( { setParameter: 1, tcmallocReleaseRate: 5.0 } )

You can also set tcmallocReleaseRate at startup time; for example:

  mongod --setParameter "tcmallocReleaseRate=5.0"

Available for both mongod and mongos.

Default: 15 seconds

Allows a server that receives a request to step up or step down, to terminate if it is unable to comply (for example due to faulty server disks) within the timeout. This enables a cluster to successfully elect a new primary node and thus continue to be available.

fassertOnLockTimeoutForStepUpDown defaults to 15 seconds. To disable nodes from fasserting, set fassertOnLockTimeoutForStepUpDown=0.

This parameter is available both at runtime and at startup:

The following example disables nodes from fasserting:

  mongod --setParameter fassertOnLockTimeoutForStepUpDown=0

Available for both mongod and mongos.

Specify an integer between 0 and 5 signifying the verbosity of the logging, where 5 is the most verbose.

The default logLevel is 0 (Informational).

This parameter is available both at runtime and at startup:

The following example sets the logLevel to 2:

  db.adminCommand( { setParameter: 1, logLevel: 2 } )

Available for both mongod and mongos.

Sets the verbosity levels of various components for log messages. The verbosity level determines the amount of Informational and Debug messages MongoDB outputs.

The verbosity level can range from 0 to 5:

For a component, you can also specify -1 to inherit the parent's verbosity level.

To specify the verbosity level, use a document similar to the following:

  {


    verbosity: <int>,


    <component1>: { verbosity: <int> },


    <component2>: {


       verbosity: <int>,


       <component3>: { verbosity: <int> }


    },


    ...


  }

For the components, you can specify just the <component>: <int> in the document, unless you are setting both the parent verbosity level and that of the child component(s) as well:

  {


    verbosity: <int>,


    <component1>: <int> ,


    <component2>: {


       verbosity: <int>,


       <component3>: <int>


    }


    ...


  }

The top-level verbosity field corresponds to systemLog.verbosity which sets the default level for all components. The default value of systemLog.verbosity is 0.

The components correspond to the following settings:

Unless explicitly set, the component has the verbosity level of its parent. For example, storage is the parent of storage.journal. That is, if you specify a storage verbosity level, this level also applies to:

This parameter is available both at runtime and at startup:

For example, the following sets the default verbosity level to 1, the query to 2, the storage to 2, and the storage.journal to 1.

  db.adminCommand( {


     setParameter: 1,


     logComponentVerbosity: {


        verbosity: 1,


        query: { verbosity: 2 },


        storage: {


           verbosity: 2,


           journal: {


              verbosity: 1


           }


        }


     }


  } )

You can also set parameter logComponentVerbosity at startup time, passing the verbosity level document as a string.

  mongod --setParameter "logComponentVerbosity={command: 3}"

mongosh also provides the db.setLogLevel() to set the log level for a single component. For various ways to set the log verbosity level, see Configure Log Verbosity Levels.

Available for both mongod and mongos.

Type: non-negative integer

Default: 10

Specifies the maximum size, in kilobytes, for an individual attribute field in a log entry; attributes exceeding this limit are truncated.

Truncated attribute fields print field content up to the maxLogSizeKB limit and excise field content past that limit, retaining valid JSON formatting. Log entries that contain truncated attributes append a truncated object to the end of the log entry.

See log message truncation for more information.

A value of 0 disables truncation entirely. Negative values for this parameter are not valid.

Using a large value, or disabling truncation with a value of 0, may adversely affect system performance and negatively impact database operations.

This parameter is available both at runtime and at startup:

The following example sets the maximum log line size to 20 kilobytes:

  mongod --setParameter maxLogSizeKB=20

Available for mongod only.

Type: boolean

Default: false

Flag that determines whether operations collect resource consumption metrics and report them in the slow query logs. If you enable profiling, these metrics are also included.

If set to true, running the explain command returns operationMetrics when the verbosity is executionStats or higher.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for both mongod and mongos.

Sets quiet logging mode. If 1, mongod will go into a quiet logging mode which will not log the following events/activities:

This parameter is available both at runtime and at startup:

Consider the following example which sets the quiet parameter to 1:

  db.adminCommand( { setParameter: 1, quiet: 1 } )

systemLog.quiet

Available for both mongod and mongos.

Type: boolean

Available in MongoDB Enterprise only.

Configure the mongod or mongos to redact any message accompanying a given log event before logging. This prevents the program from writing potentially sensitive data stored on the database to the diagnostic log. Metadata such as error or operation codes, line numbers, and source file names are still visible in the logs.

Use redactClientLogData in conjunction with Encryption at Rest and TLS/SSL (Transport Encryption) to assist compliance with regulatory requirements.

To enable log redaction at startup, you can either:

You can't use the --setParameter option to set redactClientLogData at startup.

To enable log redaction on a running mongod or mongos, use the following command:

  db.adminCommand( { setParameter: 1, redactClientLogData : true } )

security.redactClientLogData

Available for both mongod and mongos.

Type: boolean

Default: true

Configures mongod and mongos to redact field values of encrypted Binary data from all log messages.

This parameter is available both at runtime and at startup:

Available for both mongod and mongos.

Configures mongod to log full source code stack traces for every database and socket C++ exception, for use with debugging. If true, mongod will log full stack traces.

This parameter is only available at runtime. To set the parameter, use the setParameter command.

Consider the following example which sets the traceExceptions to true:

  db.adminCommand( { setParameter: 1, traceExceptions: true } )

systemLog.traceAllExceptions

Available for both mongod and mongos.

Type: boolean

Default: false

By default, a mongod or mongos with TLS/SSL enabled and net.ssl.allowConnectionsWithoutCertificates : true lets clients connect without providing a certificate for validation while logging an warning. Set suppressNoTLSPeerCertificateWarning to 1 or true to suppress those warnings.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

The following operation sets suppressNoTLSPeerCertificateWarning to true:

  db.adminCommand( { setParameter: 1, suppressNoTLSPeerCertificateWarning: true} )

Available for both mongod and mongos.

Type: boolean

Default: true

Determines whether to enable specific log messages related to cluster connection health metrics. If enableDetailedConnectionHealthMetricLogLines is set to false, the following log messages are turned off, but MongoDB still collects data on the cluster connection health metrics:

This parameter is available both at runtime and at startup:

Available for both mongod and mongos.

Type: boolean

Default: true

Determines whether to enable the collecting and logging of data for diagnostic purposes. Diagnostic logging is enabled by default.

This parameter is available both at runtime and at startup:

For example, the following disables the diagnostic collection:

  mongod --setParameter diagnosticDataCollectionEnabled=false

Available for mongos only.

Type: String

If Full Time Diagnostic Data Capture (FTDC) is disabled with diagnosticDataCollectionEnabled or if systemLog.destination is set to syslog, you must restart mongos after setting diagnosticDataCollectionDirectoryPath.

Specify the directory for the diagnostic directory for mongos. If the directory does not exist, mongos creates the directory.

If unspecified, the diagnostic data directory is computed by truncating the mongos instance's --logpath or systemLog.path file extension(s) and concatenating diagnostic.data.

For example, if mongos has --logpath /var/log/mongodb/mongos.log.201708015, then the diagnostic data directory is /var/log/mongodb/mongos.diagnostic.data/.

If the mongos cannot create the specified directory, the diagnostic data capture is disabled for that instance. mongos may not be able to create the specified directory if a file with the same name already exists in the path or if the process does not have permissions to create the directory.

This parameter is available both at runtime and at startup:

Available for both mongod and mongos.

Type: integer

Default: 200

Specifies the maximum size, in megabytes, of the diagnostic.data directory. If directory size exceeds this number, the oldest diagnostic files in the directory are automatically deleted based on the timestamp in the file name.

This parameter is available both at runtime and at startup:

For example, the following sets the maximum size of the directory to 250 megabytes:

  mongod --setParameter diagnosticDataCollectionDirectorySizeMB=250

The minimum value for diagnosticDataCollectionDirectorySizeMB is 10 megabytes. diagnosticDataCollectionDirectorySizeMB must be greater than maximum diagnostic file size diagnosticDataCollectionFileSizeMB.

Available for both mongod and mongos.

Type: integer

Default: 10

Specifies the maximum size, in megabytes, of each diagnostic file. If the file exceeds the maximum file size, MongoDB creates a new file.

This parameter is available both at runtime and at startup:

For example, the following sets the maximum size of each diagnostic file to 20 megabytes:

  mongod --setParameter diagnosticDataCollectionFileSizeMB=20

The minimum value for diagnosticDataCollectionFileSizeMB is 1 megabyte.

Available for both mongod and mongos.

Type: integer

Default: 1000

Specifies the interval, in milliseconds, at which to collect diagnostic data.

This parameter is available both at runtime and at startup:

For example, the following sets the interval to 5000 milliseconds or 5 seconds:

  mongod --setParameter diagnosticDataCollectionPeriodMillis=5000

The minimum value for diagnosticDataCollectionPeriodMillis is 100 milliseconds.

Available for both mongod and mongos.

Type: boolean

Default: false

To configure cluster nodes for split horizon DNS (https://en.wikipedia.org/wiki/Split-horizon_DNS), use host names instead of IP addresses.

Starting in MongoDB v5.0, replSetInitiate and replSetReconfig reject configurations that use IP addresses instead of hostnames.

Use disableSplitHorizonIPCheck to modify nodes that cannot be updated to use host names. The parameter only applies to the configuration commands.

mongod and mongos do not rely on disableSplitHorizonIPCheck for validation at startup. Legacy mongod and mongos instances that use IP addresses instead of host names can start after an upgrade.

Instances that are configured with IP addresses log a warning to use host names instead of IP addresses.

To allow configuration changes using IP addresses, set disableSplitHorizonIPCheck=true using the command line:

  /usr/local/bin/mongod  --setParameter disableSplitHorizonIPCheck=true -f /etc/mongod.conf

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  setParameter:


     disableSplitHorizonIPCheck: true

Available for both mongod and mongos.

Type: boolean

Default: false

If enableOverrideClusterChainingSetting is true, replica set secondary members can replicate data from other secondary members even if settings.chainingAllowed is false.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the enableOverrideClusterChainingSetting for a mongod instance to true:

  mongod --setParameter enableOverrideClusterChainingSetting=true

Available for both mongod and mongos.

Type: integer

Default: 300000 (5 minutes)

The interval (in milliseconds) at which the cache refreshes its logical session records against the main session store.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the logicalSessionRefreshMillis for a mongod instance to 10 minutes:

  mongod --setParameter logicalSessionRefreshMillis=600000

Available for both mongod and mongos.

Type: integer

Default: 30

This parameter is intended for testing purposes only and not for production use.

The time in minutes that a session remains active after its most recent use. Sessions that have not received a new read/write operation from the client or been refreshed with refreshSessions within this threshold are cleared from the cache. State associated with an expired session may be cleaned up by the server at any time.

This parameter applies only to the instance on which it is set. To set this parameter on replica sets and sharded clusters, you must specify the same value on every member; otherwise, sessions will not function properly.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the localLogicalSessionTimeoutMinutes for a test mongod instance to 20 minutes:

  mongod --setParameter localLogicalSessionTimeoutMinutes=20

Available for both mongod and mongos.

Type: integer

Default: 31536000 (1 year)

The maximum amount by which the current cluster time can be advanced; specifically, maxAcceptableLogicalClockDriftSecs is the maximum difference between the new value of the cluster time and the current cluster time. Cluster time is a logical time used for ordering of operations.

You cannot advance the cluster time to a new value if the new cluster time differs from the current cluster time by more than maxAcceptableLogicalClockDriftSecs.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the maxAcceptableLogicalClockDriftSecs for a mongod instance to 15 minutes:

  mongod --setParameter maxAcceptableLogicalClockDriftSecs=900

Available for both mongod and mongos.

Type: integer

Default: 1000000

The maximum number of sessions that can be cached.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the maxSessions for a mongod instance to 1000:

  mongod --setParameter maxSessions=1000

Available for both mongod and mongos.

Type: integer

Default: 0

The number of milliseconds to delay applying batches of oplog operations on secondary nodes. By default, oplogBatchDelayMillis is 0, meaning oplog batches are applied with no delay. When there is no delay, MongoDB may apply frequent, small oplog batches to secondaries.

Increasing oplogBatchDelayMillis causes MongoDB to apply oplog batches less frequently on secondaries, with each batch containing larger amounts of data. This reduces IOPS (Input/Output Operations Per Second) on secondaries, but adds latency for writes with write concern "majority".

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, run the following command to set the oplogBatchDelayMillis for a mongod instance to 20 milliseconds:

  mongod --setParameter oplogBatchDelayMillis=20

Available for mongod only.

Type: integer

Default: 10

The duration in seconds between noop writes on each individual node.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

To modify this value for a MongoDB Atlas (https://www.mongodb.com/docs/atlas/) cluster, you must contact Atlas Support (https://www.mongodb.com/docs/atlas/support/).

The following example sets the periodicNoopIntervalSecs to 1 second at startup:

  mongod --setParameter periodicNoopIntervalSecs=1

Available for both mongod and mongos.

Type: boolean

Default: true

Determines whether the temporary documents required for retryable findAndModify commands are stored in the side collection (config.image_collection).

If storeFindAndModifyImagesInSideCollection is:

Keep storeFindAndModifyImagesInSideCollection set to true if you:

Secondaries may experience increased CPU usage when storeFindAndModifyImagesInSideCollection is true.

This parameter is available both at runtime and at startup:

For example, to set storeFindAndModifyImagesInSideCollection to false during startup:

  mongod --setParameter storeFindAndModifyImagesInSideCollection=false

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, storeFindAndModifyImagesInSideCollection: false } )

Available for mongod only.

Type: integer

Default: 30

The minimum lifetime a transaction record exists in the transactions collection before the record becomes eligible for cleanup.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the TransactionRecordMinimumLifetimeMinutes for a mongod instance to 20 minutes:

  mongod --setParameter TransactionRecordMinimumLifetimeMinutes=20

localLogicalSessionTimeoutMinutes

Type: boolean

Default: true

Enables or disables the mechanism that controls the rate at which the primary applies its writes with the goal of keeping the secondary members' majority committed lag under a configurable maximum value.

This parameter is available both at runtime and at startup:

For flow control to engage, the replica set/sharded cluster must have: featureCompatibilityVersion (fCV) of 4.2 and read concern majority enabled. That is, enabled flow control has no effect if fCV is not 4.2 or if read concern majority is disabled.

Type: integer

Default: 10

The target maximum majority committed lag when running with flow control. When flow control is enabled, the mechanism attempts to keep the majority committed lag under the specified seconds. The parameter has no effect if flow control is disabled.

The specified value must be greater than 0.

In general, the default settings should suffice; however, if modifying from the default value, decreasing, rather than increasing, the value may prove to be more useful.

This parameter is available both at runtime and at startup:

Type: integer

Default: 10

The amount of time to wait to log a warning once the flow control mechanism detects the majority commit point has not moved.

The specified value must be greater than or equal to 0, with 0 to disable warnings.

This parameter is available both at runtime and at startup:

Type: integer

Default: 86400

The amount of time in seconds a secondary performing initial sync attempts to resume the process if interrupted by a transient network error. The default value is equivalent to 24 hours.

This parameter is available both at runtime and at startup:

Available for mongod only.

Type: String

The preferred source for performing initial sync. Specify one of the following read preference modes:

If the replica set has disabled chaining, the default initialSyncSourceReadPreference read preference mode is primary.

You cannot specify a tag set or maxStalenessSeconds to initialSyncSourceReadPreference.

If the mongod cannot find a sync source based on the specified read preference, it logs an error and restarts the initial sync process. The mongod exits with an error if it cannot complete the initial sync process after 10 attempts. For more information on sync source selection, see Initial Sync Source Selection.

initialSyncSourceReadPreference takes precedence over the replica set's settings.chainingAllowed setting when selecting an initial sync source. After a replica set member successfully completes initial sync, it defers to the value of chainingAllowed when selecting a replication sync source.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongod only.

Type: String

Default: logical

Available only in MongoDB Enterprise.

Method used for initial sync.

Set to logical to use logical initial sync. Set to fileCopyBased to use file copy based initial sync.

This parameter only affects the sync method for the member on which it is specified. Setting this parameter on a single replica set member does not affect the sync method of any other replica set members.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Type: integer

Default: 3

Sync sources are evaluated each time a sync source is updated and each time a node fetches a batch of oplog entries. If there are more than maxNumSyncSourceChangesPerHour source changes in an hour, the node temporarily stops re-evaluating that sync source. If this parameter is set with a high value, the node may make unnecessary source changes.

This parameter will not prevent a node from starting to sync from another node if it doesn't have a sync source. The node will re-evaluate if a sync source becomes invalid. Similarly, if the primary changes and chaining is disabled, the node will update to sync from the new primary.

This parameter is available both at runtime and at startup:

Available for mongod only.

Type: boolean

Default: true

Enables or disables streaming replication. Set the value to true to enable streaming replication.

Set the value to false to disable streaming replication. If disabled, secondaries fetch batches of oplog entries by issuing a request to their sync from source and waiting for a response. This requires a network roundtrip for each batch of oplog entries.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongod only.

Type: integer

Default: 60

Maximum time in seconds for a member of a replica set to wait for the find command to finish during data synchronization.

This parameter is available both at runtime and at startup:

Available for mongod only.

Type: integer

Default: 16

Maximum number of threads to use to apply replicated operations in parallel. Values can range from 1 to 256 inclusive. However, the maximum number of threads used is capped at twice the number of available cores.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

replWriterMinThreadCount

Available for mongod only.

Type: integer

Default: 0

Minimum number of threads to use to apply replicated operations in parallel. Values can range from 0 to 256 inclusive. You can only set replWriterMinThreadCount at startup and cannot change this setting with the setParameter command.

Parallel application of replication operations uses up to replWriterThreadCount threads. If replWriterMinThreadCount is configured with a value less than replWriterThreadCount, the thread pool will timeout idle threads until the total count of threads in the thread pool is equal to replWriterMinThreadCount.

replWriterMinThreadCount must be configured with a value that is less than or equal to replWriterThreadCount.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Type: 64-bit integer

Default: 86400 (1 day)

Maximum age of data that can be rolled back. Negative values for this parameter are not valid.

If the time between the end of the to-be-rolledback instance's oplog and the first operation after the common point (the last point where the source node and the to-be-rolledback node had the same data) exceeds this value, the rollback will fail.

To effectively have an unlimited rollback period, set the value to 2147483647 which is the maximum value allowed and equivalent to roughly 68 years.

This parameter is available both at runtime and at startup:

Available for mongod only.

Type: integer

Default: 10

The length of time (in milliseconds) that a secondary must wait if the afterClusterTime is greater than the last applied time from the oplog. After the waitForSecondaryBeforeNoopWriteMS passes, if the afterClusterTime is still greater than the last applied time, the secondary makes a no-op write to advance the last applied time.

This parameter is available both at runtime and at startup:

The following example sets the waitForSecondaryBeforeNoopWriteMS to 20 milliseconds:

  mongod --setParameter waitForSecondaryBeforeNoopWriteMS=20

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, waitForSecondaryBeforeNoopWriteMS: 20 } )

Available for mongod only.

Type: boolean

Default: true

Flag that determines whether MongoDB creates rollback files that contains documents affected during a rollback.

By default, createRollbackDataFiles is true and MongoDB creates the rollback files.

This parameter is available both at runtime and at startup:

The following example sets createRollbackDataFiles to false so that the rollback files are not created:

  mongod --setParameter createRollbackDataFiles=false

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, createRollbackDataFiles: false } )

For more information, see Collect Rollback Data.

Default: 104857600 (100MB)

Sets the maximum oplog application batch size in bytes.

Values can range from 16777216 (16MB) to 104857600 (100MB) inclusive.

This parameter is available both at runtime and at startup:

The following example sets replBatchLimitBytes to 64 MB to limit the oplog application batch size:

  mongod --setParameter replBatchLimitBytes=67108864

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, replBatchLimitBytes: 64 * 1024 * 1024 } )

Available for mongod only.

Type: Document

Default: { samplingRate: 0.01, maxTimeMS: 1000 }

Specifies the settings for mirrored reads for the mongod instance. The settings only take effect when the member is a primary.

The parameter mirrorReads takes a JSON document with the following fields:

This parameter is available both at runtime and at startup:

If you specify from the configuration file or on the command line, enclose the mirrorReads document in quotes.

For example, the following sets the mirror reads sampling rate to 0.10 from the command line:

  mongod --setParameter mirrorReads='{ samplingRate: 0.10 }'

Or, to specify in a configuration file:

  setParameter:


     mirrorReads: '{samplingRate: 0.10}'

Or if using the setParameter command in a mongosh session that is connected to a running mongod, do not enclose the document in quotes:

  db.adminCommand( { setParameter: 1, mirrorReads: { samplingRate: 0.10 } } )

Available for mongod only.

Type: boolean

Default: false

Specifies whether the replica set allows the use of multiple arbiters.

The use of multiple arbiters is not recommended:

For more information, see Concerns with Multiple Arbiters.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter allowMultipleArbiters=true

Available for mongod only.

Type: integer

Default: 10000000

If sampleRate and sampleSize are not set when you run analyzeShardKey, specifies the number of documents to sample when calculating shard key characteristics metrics. Must be greater than 0.

This parameter is available both at runtime and at startup:

This example sets analyzeShardKeyCharacteristicsDefaultSampleSize to 10000 at startup:

  mongod --setParameter analyzeShardKeyCharacteristicsDefaultSampleSize=10000

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, analyzeShardKeyCharacteristicsDefaultSampleSize: 10000 } )

Available for mongod only.

Type: integer

Default: 5

Specifies the number of most common shard key values to return. If the collection contains fewer unique shard keys than this value, analyzeShardKeyNumMostCommonValues returns that number of most common values. Must be greater than 0 and less than or equal to 1000.

This parameter is available both at runtime and at startup:

This example sets analyzeShardKeyNumMostCommonValues to 3 at startup:

  mongod --setParameter analyzeShardKeyNumMostCommonValues=3

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, analyzeShardKeyNumMostCommonValues: 3 } )

Available for mongod only.

Type: integer

Default: 100

Specifies the number of ranges to partition the shard key space into when calculating the hotness of shard key ranges. Must be greater than 0 and less than or equal to 10000.

This parameter is available both at runtime and at startup:

This example sets analyzeShardKeyNumRanges to 50 at startup:

  mongod --setParameter analyzeShardKeyNumRanges=50

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, analyzeShardKeyNumRanges: 50 } )

Available for mongod only.

Type: double

Default: 0.7

Specifies the RecordId correlation coefficient threshold used to determine if a shard key is monotonically changing in insertion order. Must be greater than 0 and less than or equal to 1.

This parameter is available both at runtime and at startup:

This example sets analyzeShardKeyMonotonicityCorrelationCoefficientThreshold to 1 at startup:

  mongod --setParameter analyzeShardKeyMonotonicityCorrelationCoefficientThreshold=1

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, analyzeShardKeyMonotonicityCorrelationCoefficientThreshold: 1 } )

Available for mongod only.

Type: integer

Default: 3600

When AutoMerger is enabled, specifies the amount of time between automerging rounds, in seconds. The default value is 3600 seconds, or one hour.

autoMergerIntervalSecs can only be set on config servers.

This parameter is available both at runtime and at startup:

This example sets autoMergerIntervalSecs to 7200 seconds, or two hours, at startup:

  mongod --setParameter autoMergerIntervalSecs=7200

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, autoMergerIntervalSecs: 7200 } )

Available for mongod only.

Type: integer

Default: 15000

When AutoMerger is enabled, specifies the minimum amount time between merges initiated by the AutoMerger on the same collection, in milliseconds.

autoMergerThrottlingMS can only be set on config servers.

This parameter is available both at runtime and at startup:

This example sets autoMergerThrottlingMS to 60000 milliseconds, or one minute, at startup:

  mongod --setParameter autoMergerThrottlingMS=60000

During run time, you can set or modify the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, autoMergerThrottlingMS: 60000 } )

Available for mongod only.

Type: integer

Default: 1000

Specifies the minimum amount of time between two consecutive balancing rounds. This allows you to throttle the balancing rate. This parameter only takes effect on config server nodes.

This parameter is available both at runtime and at startup:

This example sets balancerMigrationsThrottlingMs to 2000 milliseconds at startup:

  mongod --setParameter balancerMigrationsThrottlingMs=2000

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, balancerMigrationsThrottlingMs: 2000 } )

Available for both mongod and mongos.

Type: integer

Default: 0

Specifies the minimum time period (in milliseconds) between consecutive split and merge commands run by the balancer when the chunks in a sharded collection are defragmented. chunkDefragmentationThrottlingMS limits the rate of split and merge commands.

This parameter is available both at runtime and at startup:

The following example sets chunkDefragmentationThrottlingMS to 10 milliseconds:

  mongod --setParameter chunkDefragmentationThrottlingMS=10

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, chunkDefragmentationThrottlingMS: 10 } )

Available starting in MongoDB 7.0, 6.3, 6.0.6 (and 5.0.15).

Available for mongod only.

Type: integer

Default: 1

Specifies an integer that sets the number of threads on the source shard and the receiving shard for chunk migration. Chunk migrations use the number of threads that you set on the receiving shard for both the source and receiving shard.

Increasing the concurrency improves chunk migration performance, but also increases the workload and disk IOPS usage on the source shard and the receiving shard.

Maximum value is 500.

You should typically use half the total number of CPU cores as threads. For example, if the total is 16 cores, set chunkMigrationConcurrency to 8 threads (or fewer).

If chunkMigrationConcurrency is greater than 1, the _secondaryThrottle configuration setting is ignored. The _secondaryThrottle setting determines when the chunk migration proceeds with the next document in the chunk. For details, see Range Migration and Replication.

This parameter is available both at runtime and at startup:

The following example sets chunkMigrationConcurrency to 5:

  mongod --setParameter chunkMigrationConcurrency=5

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, chunkMigrationConcurrency: 5 } )

To configure collection balancing, see configureCollectionBalancing.

To learn about defragmenting sharded collections, see Defragment Sharded Collections.

Available for mongod only.

Type: boolean

Default: false

If set on a shard's primary, specifies if range deletion is paused on the shard. If set to true, cleanup of ranges containing orphaned documents is paused. The shard can continue to donate chunks to other shards, but the donated documents will not be removed from this shard until you set this parameter to false. This shard can continue to receive chunks from other shards as long as it does not have a pending range deletion task in the config.rangeDeletions collection that overlaps with the incoming chunk's range.

When disableResumableRangeDeleter is true, chunk migrations fail if orphaned documents exist on the recipient shard's primary in the same range as the incoming chunks.

The parameter has no effect on the mongod if it is not the shard's primary.

If you set disableResumableRangeDeleter parameter to true, ensure that you apply it consistently for all members in the shard's replica set. In the event of a failover, this setting's value on the new primary dictates the behavior of the range deleter.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter disableResumableRangeDeleter=false

Available for mongod only.

Type: boolean

Default: true

If set on the config server's primary, enables or disables the index consistency check for sharded collections. The parameter has no effect on the mongod if it is not the config server's primary.

This parameter is available both at runtime and at startup:

The following example sets enableShardedIndexConsistencyCheck to false for a config server primary:

  mongod --setParameter enableShardedIndexConsistencyCheck=false

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, enableShardedIndexConsistencyCheck: false } )

Available for mongos only.

Type: boolean

Default: false

Determines whether mongos performs opportunistic reads against replica sets.

When this parameter is set to true, mongos directs secondary reads to secondaries with active connections. It sends the request to the first secondary that accepts the connection. When this parameter is set to false, mongos holds secondary reads until it can establish a connection to a specific secondary, (except in the case of hedged reads).

Under certain workloads, opportunistic reads may trigger the opening of unnecessary connections from mongos to mongod and reduce overall performance. This parameter should not be enabled unless your application has a specific need for the feature.

This parameter is available both at runtime and at startup:

For example, to set opportunisticSecondaryTargeting during startup:

  mongos --setParameter opportunisticSecondaryTargeting=true

Available for mongod only.

Type: integer

Default: 600000

If set on the config server's primary, the interval, in milliseconds, at which the config server's primary checks the index consistency of sharded collections. The parameter has no effect on the mongod if it is not the config server's primary.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following sets the interval at 300000 milliseconds (5 minutes) at startup:

  mongod --setParameter shardedIndexConsistencyCheckIntervalMS=300000

Available for both mongod and mongos.

Type: boolean

Default: true

This parameter allows the catalog cache to be refreshed only if the shard needs to be refreshed. If disabled, any stale chunk will cause the entire chunk distribution for a collection to be considered stale and force all routers who contact the shard to refresh their shard catalog cache.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter enableFinerGrainedCatalogCacheRefresh=true


  mongos --setParameter enableFinerGrainedCatalogCacheRefresh=true

Starting in MongoDB 8.0, hedged reads are deprecated. Queries that specify the read preference nearest no longer use hedged reads by default. If you explicitly specify a hedged read, MongoDB performs a hedged read and logs a warning.

Available for mongos only.

Type: integer

Default: 150

Specifies the maximum time limit (in milliseconds) for the hedged read. That is, the additional read sent to hedge the read operation uses the maxTimeMS value of maxTimeMSForHedgedReads while the read operation that is being hedged uses the maxTimeMS value specified for the operation.

This parameter is available both at runtime and at startup:

For example, to set the limit to 200 milliseconds, you can issue the following during startup:

  mongos --setParameter maxTimeMSForHedgedReads=200

Or if using the setParameter command in a mongosh session that is connected to a running mongos:

  db.adminCommand( { setParameter: 1, maxTimeMSForHedgedReads: 200 } )

Available for mongod only.

Type: integer

Default: 10

For moveChunk and moveRange operations, specifies the maximum percentage of untrasferred data allowed by the migration protocol (expressed in percentage of the total chunk size) to transition from the catchup phase to the commit phase.

Setting a higher catchup percentage can decrease the amount of time it takes for the migration to complete at the cost of increased latency during concurrent upsert and delete operations.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Starting in MongoDB 7.1 (and 7.0.1), you can set the parameter during runtime.

For example, to set the maximum percentage to 20, you can issue the following during startup:

  mongod --setParameter maxCatchUpPercentageBeforeBlockingWrites=20

Starting in MongoDB 7.1 (and 7.0.1), you can set the parameter during runtime with the setParameter command:

  db.adminCommand( { setParameter: 1, maxCatchUpPercentageBeforeBlockingWrites: 20} )

Live Migration Protocol (https://github.com/mongodb/mongo/blob/master/src/mongo/db/s/README.md#the-live-migration-protocol)

Available for mongod only.

Type: integer

Default: 500

Limits the time a shard waits for a critical section within a transaction.

When a query accesses a shard, a chunk migration or DDL operation may already hold the critical section for the collection. If the query finds the critical section is taken, the shard waits until the critical section has been released. When the shard returns control to mongos, mongos retries the query. However, if a multi-shard transaction interacts with an operation that takes the critical section on multiple shards, the interaction can result in a distributed deadlock.

metadataRefreshInTransactionMaxWaitBehindCritSecMS limits the maximum time a shard waits within a transaction for the critical section to be released.

To reduce the maximum wait time for the critical section within a transaction, lower the value of metadataRefreshInTransactionMaxWaitBehindCritSecMS.

If metadataRefreshInTransactionMaxWaitBehindCritSecMS is too low, mongos could use all of its retry attempts and return an error.

This parameter is available both at runtime and at startup:

For example, to set metadataRefreshInTransactionMaxWaitBehindCritSecMS to 400 milliseconds:

  db.adminCommand( { setParameter: 1, metadataRefreshInTransactionMaxWaitBehindCritSecMS: 400 } )

Available for both mongod and mongos.

Type: integer

Default: 10

Interval that a sampler (mongos or mongod) refreshes its query analyzer sample rates.

The sample rate configured by the configureQueryAnalyzer command is divided among mongos instances in the sharded cluster or mongod instances in the replica set based on the traffic going through them. To make the sample rate assignment for a mongos or mongod more responsive to the traffic going through it, decrease this value.

We recommend using the default value.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Starting in MongoDB 7.0.1, you can set queryAnalysisSamplerConfigurationRefreshSecs during run time.

This example sets queryAnalysisSamplerConfigurationRefreshSecs to 60 seconds at startup on a mongod instance:

  mongod --setParameter queryAnalysisSamplerConfigurationRefreshSecs=60

This example sets queryAnalysisSamplerConfigurationRefreshSecs to 60 seconds at startup on a mongos instance:

  mongos --setParameter queryAnalysisSamplerConfigurationRefreshSecs=60

To set the value to 30 seconds, run the following:

  db.adminCommand( { setParameter: 1, queryAnalysisSamplerConfigurationRefreshSecs: 30 } )

Available for mongod only.

Type: integer

Default: 90

Interval that sampled queries are written to disk, in seconds.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Starting in MongoDB 7.0.1, you can set queryAnalysisWriterIntervalSecs during run time.

This example sets queryAnalysisWriterIntervalSecs to 60 seconds at startup on a mongod instance:

  mongod --setParameter queryAnalysisWriterIntervalSecs=60


  To set the value to 60 seconds, run the following:

  db.adminCommand( { setParameter: 1, queryAnalysisWriterIntervalSecs: 60 } )

Available for mongod only.

Type: integer

Default: 100 * 1024 * 1024

Maximum amount of memory in bytes that the query sampling writer is allowed to use. Once the limit is reached, all new queries and diffs are discarded from sampling until the buffer is flushed. Must be greater than 0.

This parameter is available both at runtime and at startup:

This example sets queryAnalysisWriterMaxMemoryUsageBytes to 10000000 at startup on a mongod instance:

  mongod --setParameter queryAnalysisWriterMaxMemoryUsageBytes=10000000

Available for mongod only.

Type: integer

Default: 100000

Maximum number of sampled queries to write to disk at once. Must be greater than 0 and less than or equal to 100000.

This parameter is available both at runtime and at startup:

This example sets queryAnalysisWriterMaxBatchSize to 1000 at startup on a mongod instance:

  mongod --setParameter queryAnalysisWriterMaxBatchSize=1000

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, queryAnalysisWriterMaxBatchSize: 1000 } )

Available for mongod only.

Type: integer

Default: 7 * 24 * 3600

Amount of time that a sampled query document exists before being removed by the TTL monitor, in seconds. Must be greater than 0.

This parameter is available both at runtime and at startup:

This example sets queryAnalysisSampleExpirationSecs to 691200 (8 * 24 * 3600) at startup on a mongod instance:

  mongod --setParameter queryAnalysisSampleExpirationSecs=691200

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, queryAnalysisSampleExpirationSecs: 691200 } )

Available for mongos only.

Type: string

Default: on

Specifies whether mongos supports hedged reads for those read operations whose read preference have enabled the hedged read option.

Available values are:

This parameter is available both at runtime and at startup:

For example, to turn off hedged read support for a mongos instance, you can issue the following during startup:

  mongos --setParameter readHedgingMode=off

Or if using the setParameter command in a mongosh session that is connected to a running mongos:

  db.adminCommand( { setParameter: 1, readHedgingMode: "off" } )

Available for both mongod and mongos.

Type: integer

Default: 500

Specifies the size of the routing table cache buckets used to implement chunk grouping optimization. Must be greater than 0.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, to set the cache chunk bucket size to 250 on a mongod, issue the following command at startup:

  mongod --setParameter routingTableCacheChunkBucketSize=250

Available for mongod only.

Type: integer

Default: 15000

Specifies the time (in milliseconds) to wait for any ongoing database operations to complete before initiating a shutdown of mongod in response to a SIGTERM signal.

This parameter is available both at runtime and at startup:

For example, to set the time to 250 milliseconds, you can issue the following during startup:

  mongod --setParameter shutdownTimeoutMillisForSignaledShutdown=250

Or if using the setParameter command in a mongosh session that is connected to a running mongod:

  db.adminCommand( { setParameter: 1, shutdownTimeoutMillisForSignaledShutdown: 250 } )

Available for mongos only.

Type: integer

Default: 15000

Specifies the time (in milliseconds) to wait for any ongoing database operations to complete before initiating a shutdown of mongos in response to a SIGTERM signal.

This parameter is available both at runtime and at startup:

For example, to set the time to 250 milliseconds, you can issue the following during startup:

  mongos --setParameter mongosShutdownTimeoutMillisForSignaledShutdown=250

Or if using the setParameter command in a mongosh session that is connected to a running mongos:

  db.adminCommand( { setParameter: 1, mongosShutdownTimeoutMillisForSignaledShutdown: 250 } )

Available for both mongod and mongos.

Type: integer

Default: 300000 (5 minutes)

Maximum time that mongos goes without communication to a host before mongos drops all connections to the host.

If set, ShardingTaskExecutorPoolHostTimeoutMS should be greater than the sum of ShardingTaskExecutorPoolRefreshRequirementMS and ShardingTaskExecutorPoolRefreshTimeoutMS. Otherwise, mongos adjusts the value of ShardingTaskExecutorPoolHostTimeoutMS to be greater than the sum.

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolHostTimeoutMS to 120000 during startup:

  mongos --setParameter ShardingTaskExecutorPoolHostTimeoutMS=120000

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolHostTimeoutMS: 120000 } )

Available for both mongod and mongos.

Type: integer

Default: 2

Maximum number of simultaneous initiating connections (including pending connections in setup/refresh state) each TaskExecutor connection pool can have to a mongod instance. You can set this parameter to control the rate at which mongos adds connections to a mongod instance.

If set, ShardingTaskExecutorPoolMaxConnecting should be less than or equal to ShardingTaskExecutorPoolMaxSize. If it is greater, mongos ignores the ShardingTaskExecutorPoolMaxConnecting value.

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolMaxConnecting to 20 during startup:

  mongos --setParameter ShardingTaskExecutorPoolMaxConnecting=20

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxConnecting: 20 } )

Available for both mongod and mongos.

Type: integer

Default: 2 64 - 1

Maximum number of outbound connections each TaskExecutor connection pool can open to any given mongod instance. The maximum possible connections to any given host across all TaskExecutor pools is:

  ShardingTaskExecutorPoolMaxSize * taskExecutorPoolSize

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolMaxSize to 20 during startup:

  mongos --setParameter ShardingTaskExecutorPoolMaxSize=20

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxSize: 20 } )

mongos can have up to n TaskExecutor connection pools, where n is the number of cores. See taskExecutorPoolSize.

ShardingTaskExecutorPoolMinSize

Available for both mongod and mongos.

Type: integer

Default: -1

Optional override for ShardingTaskExecutorPoolMaxSize to set the maximum number of outbound connections each TaskExecutor connection pool can open to a configuration server.

When set to:

Parameter only applies to sharded deployments.

The following example sets ShardingTaskExecutorPoolMaxSize to 2 during startup, which sets the maximum number of outbound connections each TaskExecutor connection pool can open to a configuration server to 2:

This parameter is available both at runtime and at startup:

  mongos --setParameter ShardingTaskExecutorPoolMaxSizeForConfigServers=2

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxSizeForConfigServers: 2 } )

Available for both mongod and mongos.

Type: integer

Default: 1

Minimum number of outbound connections each TaskExecutor connection pool can open to any given mongod instance.

ShardingTaskExecutorPoolMinSize connections are created the first time a connection to a new host is requested from the pool. While the pool is idle, the pool maintains this number of connections until ShardingTaskExecutorPoolHostTimeoutMS milliseconds pass without any application using that pool.

For a mongos using the warmMinConnectionsInShardingTaskExecutorPoolOnStartup parameter, the ShardingTaskExecutorPoolMinSize parameter also controls how many connections to each shard host are established on startup of the mongos instance before it begins accepting incoming client connections.

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolMinSize to 2 during startup:

  mongos --setParameter ShardingTaskExecutorPoolMinSize=2

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMinSize: 2 } )

mongos can have up to n TaskExecutor connection pools, where n is the number of cores. See taskExecutorPoolSize.

Available for both mongod and mongos.

Type: integer

Default: -1

Optional override for ShardingTaskExecutorPoolMinSize to set the minimum number of outbound connections each TaskExecutor connection pool can open to a configuration server.

When set to:

Parameter only applies to sharded deployments.

The following example sets ShardingTaskExecutorPoolMinSize to 2 during startup, which sets the minimum number of outbound connections each TaskExecutor connection pool can open to a configuration server to 2:

This parameter is available both at runtime and at startup:

  mongos --setParameter ShardingTaskExecutorPoolMinSizeForConfigServers=2

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMinSizeForConfigServers: 2 } )

Available for both mongod and mongos.

Type: integer

Default: 60000 (1 minute)

Maximum time the mongos waits before attempting to heartbeat an idle connection in the pool. An idle connection may be discarded during the refresh if the pool is above its minimum size.

If set, ShardingTaskExecutorPoolRefreshRequirementMS should be greater than ShardingTaskExecutorPoolRefreshTimeoutMS. Otherwise, mongos adjusts the value of ShardingTaskExecutorPoolRefreshTimeoutMS to be less than ShardingTaskExecutorPoolRefreshRequirementMS.

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolRefreshRequirementMS to 90000 during startup:

  mongos --setParameter ShardingTaskExecutorPoolRefreshRequirementMS=90000

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolRefreshRequirementMS: 90000 } )

Available for both mongod and mongos.

Type: integer

Default: 20000 (20 seconds)

Maximum time the mongos waits for a heartbeat before timing out the heartbeat.

If set, ShardingTaskExecutorPoolRefreshTimeoutMS should be less than ShardingTaskExecutorPoolRefreshRequirementMS. Otherwise, mongos adjusts the value of ShardingTaskExecutorPoolRefreshTimeoutMS to be less than ShardingTaskExecutorPoolRefreshRequirementMS.

This parameter is available both at runtime and at startup:

The following example sets ShardingTaskExecutorPoolRefreshTimeoutMS to 30000 during startup:

  mongos --setParameter ShardingTaskExecutorPoolRefreshTimeoutMS=30000

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolRefreshTimeoutMS: 30000 } )

Available for both mongod and mongos.

Type: string

Default: "automatic"

On a mongos instance, this parameter sets the policy that determines the minimum size limit of its connection pools to nodes within replica sets.

On a mongod instance, this parameter sets the policy that determines the minimum size limit of its connection pools to nodes within other replica sets.

Note that this parameter only manages connections for operations that are directly related to user requests and CRUD operations.

Available values are:

This parameter is available both at runtime and at startup:

The following example sets the ShardingTaskExecutorPoolReplicaSetMatching to "automatic" during startup:

  mongod --setParameter ShardingTaskExecutorPoolReplicaSetMatching="automatic"

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1,  ShardingTaskExecutorPoolReplicaSetMatching: "automatic" } )

Available for mongos only.

Type: integer

Default: 1

The number of Task Executor connection pools to use for a given mongos.

If the parameter value is 0 or less, the number of Task Executor connection pools is the number of cores with the following exceptions:

When running MongoDB 6.2 or newer on Linux, you cannot modify the taskExecutorPoolSize from the default value of 1. You may modify this parameter when running MongoDB on Windows or macOS.

The default value of taskExecutorPoolSize is 1:

This parameter is available both at runtime and at startup:

  mongos --setParameter taskExecutorPoolSize=6

Available for mongos only.

Type: boolean

Default: true

Configures a mongos instance to preload the routing table for a sharded cluster on startup. With this setting enabled, the mongos caches the cluster-wide routing table for each sharded collection as part of its startup procedure, before it begins accepting client connections.

Without this setting enabled, the mongos only loads a routing table as needed for incoming client connections, and only loads the specific routing table for the namespace of a given request.

A mongos instance with the loadRoutingTableOnStartup parameter enabled may experience longer startup times, but will result in faster servicing of initial client connections once started.

loadRoutingTableOnStartup is enabled by default.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongos only.

Type: boolean

Default: true

Configures a mongos instance to prewarm its connection pool on startup. With this parameter enabled, the mongos attempts to establish ShardingTaskExecutorPoolMinSize network connections to each shard server as part of its startup procedure, before it begins accepting client connections.

A timeout for this behavior can be configured with the warmMinConnectionsInShardingTaskExecutorPoolOnStartupWaitMS parameter. If this timeout is reached, the mongos will begin accepting client connections regardless of the size of its connection pool.

A mongos instance with this parameter enabled may experience longer startup times, but will result in faster servicing of initial client connections once started.

warmMinConnectionsInShardingTaskExecutorPoolOnStartup is enabled by default.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongos only.

Type: integer

Default: 2000 (2 seconds)

Sets the timeout threshold in milliseconds for a mongos to wait for ShardingTaskExecutorPoolMinSize connections to be established per shard host when using the warmMinConnectionsInShardingTaskExecutorPoolOnStartup parameter. If this timeout is reached, the mongos will begin accepting client connections regardless of the size of its connection pool.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for mongod only.

Type: Non-negative integer

Default: 0

Time in milliseconds to wait between batches of insertions during cloning step of the migration process. This wait is in addition to the secondaryThrottle.

The default value of 0 indicates no additional wait.

This parameter is available both at runtime and at startup:

The following sets the migrateCloneInsertionBatchDelayMS to 200 milliseconds:

  mongod --setParameter migrateCloneInsertionBatchDelayMS=200

The parameter may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, migrateCloneInsertionBatchDelayMS: 200 } )

Available for mongod only.

Type: Non-negative integer

Default: 0

The maximum number of documents to insert in a single batch during the cloning step of the migration process.

The default value of 0 indicates no maximum number of documents per batch. However, in practice, this results in batches that contain up to 16 MB of documents.

This parameter is available both at runtime and at startup:

The following sets the migrateCloneInsertionBatchSize to 100 documents:

  mongod --setParameter migrateCloneInsertionBatchSize=100

The parameter may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, migrateCloneInsertionBatchSize: 100 } )

Available for mongod only.

Default: 900 (15 minutes)

Minimum delay before a migrated chunk is deleted from the source shard.

Before deleting the chunk during chunk migration, MongoDB waits for orphanCleanupDelaySecs or for in-progress queries involving the chunk to complete on the shard primary, whichever is longer.

However, because the shard primary has no knowledge of in-progress queries run on the shard secondaries, queries that use the chunk but are run on secondaries may see documents disappear if these queries take longer than the time to complete the shard primary queries and the orphanCleanupDelaySecs.

This behavior only affects in-progress queries that start before the chunk migration. Queries that start after the chunk migration starts will not use the migrating chunk.

If a shard has storage constraints, consider reducing this value temporarily. If running queries that exceed 15 minutes on shard secondaries, consider increasing this value.

This parameter is available both at runtime and at startup:

The following sets the orphanCleanupDelaySecs to 20 minutes:

  mongod --setParameter orphanCleanupDelaySecs=1200

This may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, orphanCleanupDelaySecs: 1200 } )

In all versions, the new value of orphanCleanupDelaySecs is only applied to range deletions created after the value is changed. To apply the new value to existing range deletions, force a step down.

Available for mongod only.

Type: Integer

Default: 1000

To route and serve operations, shards must know the routing and ownership information associated with their collections. This information propogates from a shard's primary node to its secondary nodes through the replication of the internal cache collections config.cache.collections and config.cache.chunks.<collectionName>.

In previous versions, updates on the chunk cache collection were performed individually (meaning that an entry was deleted and a new entry was inserted). Starting in MongoDB 7.2, these updates are performed as a batch of deletions followed by a batch of insertions. The updated logic improves performance for collections that contain a large number of chunks.

The persistedChunkCacheUpdateMaxBatchSize parameter specifies the maximum batch size used for updating the persisted chunk cache.

This parameter is available both at runtime and at startup:

The following example sets persistedChunkCacheUpdateMaxBatchSize to 700 at startup:

  mongod --setParameter persistedChunkCacheUpdateMaxBatchSize=700

You can also set persistedChunkCacheUpdateMaxBatchSize during runtime:

  db.adminCommand( { setParameter: 1, persistedChunkCacheUpdateMaxBatchSize: 700 } )

Available for mongod only.

Type: Non-negative integer

Default: 20

The amount of time in milliseconds to wait before the next batch of deletion during the cleanup stage of range migration (or the cleanupOrphaned command).

The _secondaryThrottle replication delay occurs after each batch deletion.

This parameter is available both at runtime and at startup:

The following sets the rangeDeleterBatchDelayMS to 200 milliseconds:

  mongod --setParameter rangeDeleterBatchDelayMS=200

The parameter may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, rangeDeleterBatchDelayMS: 200 } )

In versions prior to 6.0.3, the new value of rangeDeleterBatchDelayMS is only applied to range deletions created after the value is changed. To apply the new value to existing range deletions, force a step down.

From 6.0.3 on, the new value of the parameter is applied to all the range deletions processed after the update, regardless of when the range deletion was created.

Available for mongod only.

Type: Non-negative integer

Default: 2147483647 starting in MongoDB 5.1.2 and 5.0.6

The maximum number of documents in each batch to delete during the cleanup stage of range migration (or the cleanupOrphaned command).

A value of 0 indicates that the system chooses the default value.

This parameter is available both at runtime and at startup:

The following example sets rangeDeleterBatchSize to 32 documents:

  mongod --setParameter rangeDeleterBatchSize=32

The parameter may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, rangeDeleterBatchSize: 32 } )

In versions prior to 6.0.3, the new value of rangeDeleterBatchSize is only applied to range deletions created after the value is changed. To apply the new value to existing range deletions, force a step down.

From 6.0.3 on, the new value of the parameter is applied to all the range deletions processed after the update, regardless of when the range deletion was created.

Available for mongod only.

Type: boolean

Default: false

When true, prioritizes cleanup of orphaned documents over user operations. By default, this is set to false to prioritize user operations over cleanup of orphaned documents.

This parameter is available both at runtime and at startup:

The following example sets rangeDeleterHighPriority to true:

  mongod --setParameter rangeDeleterHighPriority=true

The parameter may also be set using the setParameter command:

  db.adminCommand( { setParameter: 1, rangeDeleterBatchSize: true } )

Available for mongod only.

Type: boolean

Default: false

When true, allows for starting a shard member or config server member as a standalone for maintenance operations. This parameter is mutually exclusive with the --configsvr or --shardsvr options.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter skipShardingConfigurationChecks=true

Once maintenance has completed, remove the skipShardingConfigurationChecks parameter when restarting the mongod.

Available for both mongod and mongos.

Type: Non-negative integer

Default: 900000

The timeout in milliseconds for find operations on chunks.

If there is a large number of chunks in the cluster and chunk loading fails with the error ExceededTimeLimit, increase the parameter value:

  mongod --setParameter findChunksOnConfigTimeoutMS=1000000

This parameter is available both at runtime and at startup:

Available for mongos only.

Type: Document

The amount of time to wait from a Health Managers Overview failure until the mongos is removed from the cluster, in seconds.

When a failure is detected and a Health Manager is configured as critical, the server waits for the specified interval before removing the mongos from the cluster.

This parameter is available both at runtime and at startup:

For example, to set the duration from failure to crash to five minutes, issue the following at startup:

  mongos --setParameter activeFaultDurationSecs=300

Or if using the setParameter command in a mongosh session that is connected to a running mongos:

  db.adminCommand(


    {


        setParameter: 1,


        activeFaultDurationSecs: 300


    }


  )

Parameters set with setParameter do not persist across restarts. See the setParameter page for details.

To make this setting persistent, set activeFaultDurationSecs in your mongos config file using the setParameter option as in the following example:

  setParameter:


     activeFaultDurationSecs: 300

Available for mongos only.

Type: Array of documents

Use this parameter to set intensity levels for Health Managers.

This parameter is available both at runtime and at startup:

healthMonitoringIntensities accepts an array of documents, values. Each document in values takes two fields:

•

•

•

•

•

•

•

•

  mongos --setParameter 'healthMonitoringIntensities={ values:[ { type:"dns", intensity: "critical"} ] }'

  db.adminCommand(


    {


        setParameter: 1,


        healthMonitoringIntensities: { values: [ { type: "dns", intensity: "critical" } ] } } )


    }


  )

  setParameter:


     healthMonitoringIntensities: "{ values:[ { type:

Available for mongos only.

Type: Array of documents

How often this Health Manager will run, in milliseconds.

This parameter is available both at runtime and at startup:

healthMonitoringIntervals accepts an array of documents, values. Each document in values takes two fields:

•

•

•

•

  mongos --setParameter 'healthMonitoringIntervals={ values:[ { type:"ldap", interval: "30000"} ] }'

  db.adminCommand(


    {


        setParameter: 1,


        healthMonitoringIntervals: { values: [ { type: "ldap", interval: "30000" } ] } } )


    }


  )

  setParameter:


     healthMonitoringIntervals: "{ values: [{type:

Available for mongos only.

Type: Document

Progress Monitor runs tests to ensure that Health Manager checks do not become stuck or unresponsive. Progress Monitor runs these tests in intervals specified by interval. If a health check begins but does not complete within the timeout given by deadline, Progress Monitor stops the mongos and removes it from the cluster.

This parameter is available both at runtime and at startup:

•

•

•

  mongos --setParameter 'progressMonitor={"interval": 1000, "deadline": 300}'

  db.adminCommand(


    {


        setParameter: 1,


        progressMonitor: { interval: 1000, deadline: 300 } )


    }


  )

  setParameter:


     progressMonitor: "{ interval: 1000, deadline: 300 }"

Available for mongod only.

Default: false

If honorSystemUmask is set to true, new files created by MongoDB have permissions in accordance with the user's umask settings. You cannot set processUmask if honorSystemUmask is set to true.

If honorSystemUmask is set to false, new files created by MongoDB have permissions set to 600, which gives read and write permissions only to the owner. New directories have permissions set to 700. You can use processUmask to override the default permissions for groups and other users on all new files created by MongoDB.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

  mongod --setParameter honorSystemUmask=true

honorSystemUmask is not available on Windows systems.

Available for mongod only.

Specify an integer between 1 and 500 signifying the number of milliseconds (ms) between journal commits.

This parameter is available both at runtime and at startup:

Consider the following example which sets the journalCommitInterval to 200 ms:

  db.adminCommand( { setParameter: 1, journalCommitInterval: 200 } )

storage.journal.commitIntervalMs

Available for mongod only.

Default: 300

The minimum time window in seconds for which the storage engine keeps the snapshot history. If you query data using read concern "snapshot" and specify an atClusterTime value older than the specified minSnapshotHistoryWindowInSeconds, mongod returns a SnapshotTooOld error.

This parameter is available both at runtime and at startup:

Specify an integer greater than or equal to (>=) 0.

Consider the following example which sets the minSnapshotHistoryWindowInSeconds to 600 seconds:

  db.adminCommand( { setParameter: 1, minSnapshotHistoryWindowInSeconds: 600 } )

Increasing the value of minSnapshotHistoryWindowInSeconds increases disk usage. For more information, see Snapshot History Retention.

To modify this value for a MongoDB Atlas (https://www.mongodb.com/docs/atlas/) cluster, you must contact Atlas Support (https://www.mongodb.com/docs/atlas/support/).

Available for mongod only.

Overrides the default permissions used for groups and other users when honorSystemUmask is set to false. By default, when honorSystemUmask is set to false, new files created by MongoDB have permissions set to 600. Use the processUmask parameter to override this default with a custom umask value. The file owner inherits permissions from the system umask.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

You cannot set this parameter if honorSystemUmask is set to true.

Consider the following example, which sets the permissions for groups and other users to read/write only and retains the system umask settings for the owner:

  mongod --setParameter processUmask=011

processUmask is not available on Windows systems.

Available for mongod only.

Type: integer

Default: 128

Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only.

Specify the maximum number of concurrent read transactions (read tickets) allowed into the storage engine.

If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128.

Starting in MongoDB 7.0, if you set storageEngineConcurrentReadTransactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transactions.

This parameter is available both at runtime and at startup:

  db.adminCommand( { setParameter: 1, storageEngineConcurrentReadTransactions: <int> } )

The wiredTigerConcurrentReadTransactions parameter was renamed to storageEngineConcurrentReadTransactions.

wiredTiger.concurrentTransactions

Available for mongod only.

Type: integer

Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only.

Specify the maximum number of concurrent write transactions allowed into the WiredTiger storage engine.

By default, MongoDB sets storageEngineConcurrentWriteTransactions to whichever value is higher:

If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128.

Starting in MongoDB 7.0, if you set storageEngineConcurrentWriteTransactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transactions.

This parameter is available both at runtime and at startup:

  db.adminCommand( { setParameter: 1, storageEngineConcurrentWriteTransactions: <int> } )

The wiredTigerConcurrentWriteTransactions parameter was renamed to storageEngineConcurrentWriteTransactions.

wiredTiger.concurrentTransactions

Available for mongod only.

Specify the interval in seconds when mongod flushes its working memory to disk. By default, mongod flushes memory to disk every 60 seconds. In almost every situation you should not set this value and use the default setting.

This parameter is available both at runtime and at startup:

Consider the following example which sets the syncdelay to 60 seconds:

  db.adminCommand( { setParameter: 1, syncdelay: 60 } )

To provide durable data, WiredTiger uses checkpoints. For more details, see Journaling and the WiredTiger Storage Engine.

Available for mongod only.

Specifies the initial delay before retying a write operation that was rolled back due to cache pressure.

In rare circumstances, a write can fail due to cache pressure. When this happens MongoDB issues a TemporarilyUnavailable error and increments the temporarilyUnavailableErrors counter in two places: the slow query log and the Full Time Diagnostic Data Capture (FTDC).

Individual operations within multi-document transactions never return TemporarilyUnavailable errors.

Adjust the write retry properties by modifying the temporarilyUnavailableBackoffBaseMs and temporarilyUnavailableMaxRetries parameters.

The parameter accepts:

This parameter is available both at runtime and at startup:

To set a new value, use db.adminCommand():

  db.adminCommand( { setParameter: 1, temporarilyUnavailableBackoffBaseMs: 3 } )

Available for mongod only.

Specifies the maximum number of retries when a write operation is rolled back due to cache pressure.

In rare circumstances, a write can fail due to cache pressure. When this happens MongoDB issues a TemporarilyUnavailable error and increments the temporarilyUnavailableErrors counter in two places: the slow query log and the Full Time Diagnostic Data Capture (FTDC).

Individual operations within multi-document transactions never return TemporarilyUnavailable errors.

Adjust the write retry properties by modifying the temporarilyUnavailableBackoffBaseMs and temporarilyUnavailableMaxRetries parameters.

The parameter accepts:

This parameter is available both at runtime and at startup:

To set a new value, use db.adminCommand():

  db.adminCommand( { setParameter: 1, temporarilyUnavailableMaxRetries: 5 } )

Available for mongod only.

Type: integer

Default: 128

Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only.

Specify the maximum number of concurrent read transactions (read tickets) allowed into the storage engine.

If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128.

Starting in MongoDB 7.0, if you set wiredTigerConcurrentReadTransactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transactions.

This parameter is available both at runtime and at startup:

  db.adminCommand( { setParameter: 1, wiredTigerConcurrentReadTransactions: <int> } )

wiredTiger.concurrentTransactions

Available for mongod only.

Type: integer

Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only.

Specify the maximum number of concurrent write transactions allowed into the WiredTiger storage engine.

By default, MongoDB sets wiredTigerConcurrentWriteTransactions to whichever value is higher:

If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128.

Starting in MongoDB 7.0, if you set wiredTigerConcurrentWriteTransactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transactions.

This parameter is available both at runtime and at startup:

  db.adminCommand( { setParameter: 1, wiredTigerConcurrentWriteTransactions: <int> } )

wiredTiger.concurrentTransactions

Available for mongod only.

Specify wiredTiger storage engine configuration options for a running mongod instance.

This parameter is only available at runtime. To set the parameter, use the setParameter command.

Avoid modifying the wiredTigerEngineRuntimeConfig unless under the direction from MongoDB engineers as this setting has major implication across both WiredTiger and MongoDB.

Consider the following operation prototype:

  db.adminCommand({


     "setParameter": 1,


     "wiredTigerEngineRuntimeConfig": "<option>=<setting>,<option>=<setting>"


  })

Available for mongod only.

Type: integer

Default: 600

Specifies the amount of time in seconds that a file handle in wiredTiger can remain idle before being closed.

If you set wiredTigerFileHandleCloseIdleTime to 0, idle handles are not closed.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example:

  mongod --setParameter wiredTigerFileHandleCloseIdleTime=100000

Available for both mongod and mongos.

Type: boolean

Default: false

Available only in MongoDB Enterprise (http://www.mongodb.com/products/mongodb-enterprise-advanced?tck=docs_server) and MongoDB Atlas (https://cloud.mongodb.com/user#/atlas/login).

Enables the auditing of authorization successes for the authCheck action.

When auditAuthorizationSuccess is false, the audit system only logs the authorization failures for authCheck.

This parameter is available both at runtime and at startup:

To enable the audit of authorization successes, issue the following command:

  db.adminCommand( { setParameter: 1, auditAuthorizationSuccess: true } )

Enabling auditAuthorizationSuccess degrades performance more than logging only the authorization failures.

If runtime audit configuration is enabled, the auditAuthorizationSuccess parameter should not appear in the mongod or mongos configuration file. The server will fail to start if the parameter is present.

getParameter

Type: integer

Default: 300

A sharded cluster may have servers which maintain audit configuration settings for the cluster. Set the interval, in seconds, for non-configured servers to poll a config server for the current audit generation. If this value returned differs from the previously known value, the initiating node will request the current configuration and update its internal state.

Using the default value of 300 seconds, non-config nodes may lag up to 5 minutes after you set the auditConfig cluster parameter.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

Available for both mongod and mongos.

Type: string

Available only in MongoDB Enterprise (http://www.mongodb.com/products/mongodb-enterprise-advanced?tck=docs_server). MongoDB Enterprise and Atlas have different configuration requirements.

Path and file name for logging metadata audit headers for audit log encryption. A header is placed at the top of each audit log file and contains metadata for decrypting the audit log. The headers are also stored in the audit log.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

For example, the following sets the path and file for auditEncryptionHeaderMetadataFile:

  mongod --setParameter auditEncryptionHeaderMetadataFile=/auditFiles/auditHeadersMetadataFile.log

Available for both mongod and mongos.

Type: boolean

Default: false

Available only in MongoDB Enterprise (http://www.mongodb.com/products/mongodb-enterprise-advanced?tck=docs_server). MongoDB Enterprise and Atlas have different configuration requirements.

Enables audit log encryption for Key Management Interoperability Protocol (KMIP) servers that only support KMIP protocol version 1.0 or 1.1.

This parameter is only available at startup. To set the parameter, use the setParameter setting.

The following example sets auditEncryptKeyWithKMIPGet to true:

  mongod --setParameter auditEncryptKeyWithKMIPGet=true

Updated in version 6.1

Available for mongod only.

Type: boolean

Default: false

This parameter is available both at runtime and at startup:

The following example sets coordinateCommitReturnImmediatelyAfterPersistingDecision to true:

  mongod --setParameter coordinateCommitReturnImmediatelyAfterPersistingDecision=true

During run time, you can also set the parameter with the setParameter command:

  db.adminCommand( { setParameter: 1, coordinateCommitReturnImmediatelyAfterPersistingDecision: true } )

Available for both mongod and mongos.

Default: 1000

Session limit for internal session metadata deletion. The metadata:

When the number of internal sessions is greater than internalSessionsReapThreshold, the metadata is deleted.

If you set internalSessionsReapThreshold to 0, the internal session metadata is only deleted when the user session ends.

This parameter is available both at runtime and at startup:

The following example sets internalSessionsReapThreshold to 500 sessions:

  db.adminCommand( { setParameter: 1, internalSessionsReapThreshold: 500 } )

You can also set internalSessionsReapThreshold at startup. For example:

  mongod --setParameter internalSessionsReapThreshold=500

Available for mongod only.

Default: 60

Specifies the lifetime of multi-document transactions. Transactions that exceed this limit are considered expired and will be aborted by a periodic cleanup process. The cleanup process runs every transactionLifetimeLimitSeconds/2 seconds or at least once every 60 seconds.

The cleanup process helps relieve storage cache pressure.

The minimum value for transactionLifetimeLimitSeconds is 1 second.

This parameter is available both at runtime and at startup:

The following sets the transactionLifetimeLimitSeconds to 30 seconds:

  db.adminCommand( { setParameter: 1, transactionLifetimeLimitSeconds: 30 } )

You can also set parameter transactionLifetimeLimitSeconds at startup time.

  mongod --setParameter "transactionLifetimeLimitSeconds=30"

To set the parameter for a sharded cluster, the parameter must be modified for all shard replica set members.

Starting in MongoDB 5.0, if you change the transactionLifetimeLimitSeconds parameter, you must also change transactionLifetimeLimitSeconds to the same value on all config server replica set members. Keeping this value consistent:

Available for mongod only.

Type: decimal

Default: 0.75

The threshold value for retrying transactions that fail due to cache pressure. The value is a percentage of the dirty cache size. The default value, 0.75, means 75% of the dirty cache.

The dirty cache is limited to 20% of the total cache size. When transactionTooLargeForCacheThreshold is set to 0.75, the server only retries transactions that use less than 15% (0.75 * 20%) of the total storage engine cache.

The limit only applies to retries. Large transactions can use more than transactionTooLargeForCacheThreshold percent of the dirty cache. However, if a large transaction is rolled back due to cache pressure, the server issues a TransactionTooLargeForCache error and does not retry the transaction.

To disable this behavior, set transactionTooLargeForCacheThreshold to 1.0.

This parameter is available both at runtime and at startup:

For more information on WiredTiger storage, see: storage.wiredTiger Options.

Available for mongod only.

Type: integer

Default: 5

The maximum amount of time in milliseconds that multi-document transactions should wait to acquire locks required by the operations in the transaction.

If the transaction cannot acquire the locks after waiting maxTransactionLockRequestTimeoutMillis, the transaction aborts.

By default, multi-document transactions wait 5 milliseconds. That is, if the transaction cannot acquire the locks within 5 milliseconds, the transaction aborts. If an operation provides a greater timeout in a lock request, maxTransactionLockRequestTimeoutMillis overrides the operation-specific timeout.

You can set maxTransactionLockRequestTimeoutMillis to:

This parameter is available both at runtime and at startup:

The following sets the maxTransactionLockRequestTimeoutMillis to 20 milliseconds:

  db.adminCommand( { setParameter: 1, maxTransactionLockRequestTimeoutMillis: 20 } )

You can also set this parameter during start-up:

  mongod --setParameter maxTransactionLockRequestTimeoutMillis=20

Available for mongod only.

Type: string

Default: 5%

Although the planCacheSize parameter existed in prior versions of MongoDB, it had no effect on the plan cache until version 6.3.

Sets the size of the plan cache only for the slot-based query execution engine.

You can set the planCacheSize value to either:

Increasing the plan cache size adds more cached query shapes for the query planner. This can improve query performance, but increases memory usage.

This parameter is available both at runtime and at startup:

The following startup command sets planCacheSize to 80 megabytes:

  mongod --setParameter planCacheSize="80MB"

You can also use the setParameter command within the MongoDB Shell (https://www.mongodb.com/docs/mongodb-shell/):

  db.adminCommand( { setParameter: 1, planCacheSize: "80MB" } )