Oracle Background Process

To maximize performance and accommodate many users, a multiprocess Oracle system uses some additional Oracle processes called background processes.

There are many types of Oracle background processes. Each performs a specific job in helping
to manage the instance. Five Oracle background processes are required, and several background processes are optional.

Required Oracle Background Processes
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1)System Monitor (SMON): Performs instance recovery following an instance crash, coalesces free space in the database, and manages space used for sorting.

2)Process Monitor (PMON): Cleans up failed user database connections.

3)Database Writer (DBWn): Writes modified database blocks from the SGA’s Database Buffer Cache to the datafiles on disk

4)Log Writer (LGWR): Writes transaction recovery information from the SGA’s Redo Log Buffer to the online Redo Log files on disk.

5)Checkpoint (CKPT): Updates the database files following a Checkpoint Event.

Optional Database Background Processes

1)Recoverer Process (RECO)

2)Job Queue Processes

3)Archiver Processes (ARCn)

4)Queue Monitor Processes (QMNn)

5)Other Background Processes