ROLLBACK [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]
Optional key words. They have no effect.
If AND CHAIN is specified, a new transaction is immediately started with the same transaction characteristics (see SET TRANSACTION (SET_TRANSACTION(7))) as the just finished one. Otherwise, no new transaction is started.
Issuing ROLLBACK outside of a transaction block emits a warning and otherwise has no effect. ROLLBACK AND CHAIN outside of a transaction block is an error.