I moved this question from stackoverflow to here as it was marked on hold as off-topic. On Oracle 10g2 DB I have set up multiple event triggered DMBS_SCHEDULER jobs and all of them are subscribed for the same event queue. The problem is when I call the function that enqueues the message in the advanced queue, therefore triggering the scheduler event all of the subscribed jobs are executed only once.

  • In the loop I am calling procedure that enqueues the messages in the queue. (I did check the message count in the queue and it matches the loop count);

  • There are multiple jobs (or a single job - I did test both cases the result is the same) that have event schedule and are subscribed to the particular queue;

  • After executing this loop, I do check the message count in the queue and the instance count of the new jobs in sys.dba_scheduler_job_log. Result - all the messages in the queue have been processed (meaning it is empty) and only one instance per each job have been registered in scheduler_job_log table;

  • The thing is that if I add DBMS_LOCK.sleep(1); after at the end of the each iteration in the loop then all of the job instances are registered in the scheduler_log_table fine.

Why do all of the other queue messages processed from the queue without running the job? Are there any DBMS_SCHEDULER settings to be adjusted?

  • I'd try the forums at Oracle Technet -- much more experience of this sort of thing there. Jul 8, 2013 at 23:49

2 Answers 2


This is a documented behavior so "it's not a bug, it's a feature".

http://docs.oracle.com/cd/B19306_01/server.102/b14231/scheduse.htm#CHDIAJEB says:

events that occur while the job is already running are ignored; the event gets consumed, but does not trigger another run of the job.

  • 1
    Thank you for pointing to this note. I did not somehow notice it when reading docs. As these event triggered jobs are not reliable in 10g and there are no company plans to migrate to 11g, then I had to think of some workaround. I changed these jobs to execute with a time period schedule (every minute), and they are calling and extra procedure that is checking and dequeueing these event messages and then processing business logic.
    – skujins
    Jul 22, 2013 at 16:06
  • Hmm "not reliable". Isn't it possible to have a plain and simple stored procedure (not a job) that is notified on each enqueue? I never tested this, so I cannot vouch, but I would say it is a traditional way and would be reliable (that is, it wouldn't silently dequeue events).
    – kubanczyk
    Jul 24, 2013 at 20:44

And this documented behaviour can be bypassed by setting this attribute to the job before its enabled:

DBMS_SCHEDULER.set_attribute ('my_job_name', 'parallel_instances', TRUE);

  • 2
    Unfortunately this attribute is only available from Oracle 11GR2.
    – skujins
    Feb 24, 2014 at 21:41

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