SMON or System Monitor Processback,”Performs critical tasks such as instance recovery and dead transaction recovery, and maintenance tasks such as temporary space reclamation, data dictionary cleanup, and undo tablespace managementSMON performs many database maintenance tasks, including the following:* Creates and manages the temporary tablespace metadata* Reclaims space used by orphaned temporary segments* Maintains the undo tablespace by onlining, offlining, and shrinking the undo segments based on undo space usage statistics* Cleans up the data dictionary when it is in a transient and inconsistent state* Maintains the SCN to time mapping table used to support Oracle Flashback featuresIn an Oracle RAC database
the SMON process of one instance can perform instance recovery for other instances that have failed.SMON is resilient to internal and external errors raised during background activities.”