SMON:          

Server monitor: recovers unused temp segments, coalesces continues free segments,

performs instance recovery.

 

PMON:

Process monitor: cleans failed transactions. If instance crashes PMON: rollback any uncommitted transactions.

 

DBWR:

Dirty buffer writer: writes modified buffer cache to datafiles; not at

commit but when more space is needed in SGA.

 

LGWR:          

ora_lgwr_SID: log writer: writes redo log buffers to redo log files on a

commit.

 

CKPT:           

ora_ckpt_SID: check point. Writes SCN to datafiles headers &

controlfiles. On 7 this is LGWR’s job.

 

ARCH:          

ora_arc0_SID, ora_arc1_SID: archiver. Copies filled redo log files to

archive log dest.

 

RECO:           

ora_reco0_SID: recover. Recovers failed distributed transactions .

 

SNPnn:          

Snapshot: check & execute jobs from the job queue (dbms_jobs) also

refresh snapshots.

 

Dmm & Snn   

MTS or shared server: ora_d000_SID, ora_d001_SID: when you have two

dispatchers. Ora_s000_SID: these are the actual shared server processes.

 

Ora_i[some number]_SID:

slave database writers.

 

Ora_qmn_SID:       

Queue monitor process. Advanced queuing.

 

Ora_p000_SID:       

Parallel query.

 

Ora_cjq_SID:

is a part of job_queue_processes, cjq0 being the coordinator. Cjq0 dynamically spawns job queue slave processes (j000 to j999) which perform actions (jobs), jobs are defined through dbms_job. The coordinator cjq0 does not start if init parameter job_queue_processes is set to 0.