In Oracle alert log, you may see below message:
Starting background process CJQ0
Thu Feb 03 10:38:40 2011
CJQ0 started with pid=48, OS id=15990882
......
Thu Feb 03 11:19:38 2011
Stopping background process CJQ0
CJQ0 is a coordinator job queue (CJQ0) process to run scheduled jobs defined by DBMS_JOB package. Oracle slave processes (J000 – J999) executes the scheduled jobs. The CJQ0 process will be keeping track of the schedule and starts slave processes so as to execute the scheduled jobs.
Normally, parameter job_queue_processes is not set to zero as it will disable all job queue processing and stop the CJQ0 process. It is suggested to set job_queue_processes to a value higher than the maximum number of simultaneous jobs you expect to run.
In troubleshooting, you might kill the process at OS level by using below query to identify SID and SPID values:
SQL> SELECT A1.SID, A2.SPID FROM V$SESSION A1,V$PROCESS A2
WHERE A1.PADDR = A2.ADDR AND TYPE='BACKGROUND'
AND A1.PROGRAM LIKE '%CJQ%'
To get the description on all Oracle background processes, run below query in the database:
SQL> select name, description from v$bgprocess;
