5 mandatory Oracle Background Processes

System Monitor SMON: Performs instance recovery following an instance crash, coalesces
free space in the database, and manages space used for sorting

Process Monitor PMON: Cleans up failed user database connections

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

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

Checkpoint CKPT : Updates the database files following a Checkpoint Event


On Unix systems, you can view these background processes from the operating system using
the ps command, as shown here:

$ ps -ef grep MARS

oracle 3969 1 0 10:02 ? 00:00:05 ora_pmon_MARS
oracle 3971 1 0 10:02 ? 00:00:00 ora_mman_MARS
oracle 3973 1 0 10:02 ? 00:00:07 ora_dbw0_MARS
oracle 3975 1 0 10:02 ? 00:00:07 ora_lgwr_MARS
oracle 3977 1 0 10:02 ? 00:00:10 ora_ckpt_MARS
oracle 3979 1 0 10:02 ? 00:00:20 ora_smon_MARS
oracle 3981 1 0 10:02 ? 00:00:00 ora_reco_MARS
oracle 3983 1 0 10:02 ? 00:00:09 ora_cjq0_MARS
oracle 3985 1 0 10:02 ? 00:00:00 ora_d000_MARS
oracle 3987 1 0 10:02 ? 00:00:00 ora_s000_MARS
oracle 4052 1 0 10:02 ? 00:00:00 ora_qmnc_MARS
oracle 4054 1 0 10:02 ? 00:00:29 ora_mmon_MARS
oracle 4057 1 0 10:02 ? 00:00:08 ora_mmnl_MARS
oracle 4059 1 0 10:02 ? 00:01:04 ora_j000_MARS
oracle 27544 1 0 20:29 ? 00:00:00 ora_q000_MARS

This output shows that 15 background processes are running on the Unix server for the MARS
database.