If it usually works then it's not likely it's a Scheduler bug.
Have you checked the run details of yuor job to see when it actually started:
SELECT log_date, job_name, status, actual_start_date, run_duration, additional_info
WHERE job_name = '&your_job'
ORDER BY log_date DESC;
If it ran at the expected time then the problem is probably in your copy procedure.
Thank you GregV. Well it did start on the expected time but it got hung!...it completed in 20 seconds today but took more than 7 hours yesterday causing an outage! There is no obvious reason that we can find here. Please see below the timings: We are at a loss to understand what may have happened here:
LOG_DATE JOB_NAME STATUS ACTUAL_START_DATE OWNER RUN_DURATION ADDITIONAL_INFO 3/28/2014
3:00:37.631963 AM -04:00
scheduled_job1 SUCCEEDED 3/28/2014
2:00:00.479827 AM -05:00
SCOTT +00 00:00:20.000000 3/27/2014 10:32:51.039442 AM -04:00 scheduled_job1 STOPPED 3/27/2014
2:00:00.437910 AM -05:00
SCOTT +00 07:32:51.000000 REASON="Stop job
called by user: 'SYS'"
3:00:29.910672 AM -04:00
scheduled_job1 SUCCEEDED 3/26/2014
2:00:00.236187 AM -05:00
SCOTT +00 00:00:30.000000 3/25/2014
3:00:31.671558 AM -04:00
scheduled_job1 SUCCEEDED 3/25/2014
2:00:00.166233 AM -05:00
SCOTT +00 00:00:31.000000 3/24/2014
3:00:28.187225 AM -04:00
scheduled_job1 SUCCEEDED 3/24/2014
2:00:01.056921 AM -05:00
SCOTT +00 00:00:27.000000 3/23/2014
3:00:28.808667 AM -04:00
scheduled_job1 SUCCEEDED 3/23/2014
2:00:00.933849 AM -05:00
SCOTT +00 00:00:28.000000 3/22/2014
3:00:24.646177 AM -04:00
scheduled_job1 SUCCEEDED 3/22/2014
2:00:00.842851 AM -05:00
SCOTT +00 00:00:24.000000 3/21/2014
3:00:22.093396 AM -04:00
scheduled_job1 SUCCEEDED 3/21/2014
2:00:00.652885 AM -05:00
SCOTT +00 00:00:21.000000
Thank you again GregV. Can you help me with more details - I mean from AWR how can we find out about locks? I used AWR basically for top sql etc. Actually it was this session that was causing locks. It caused nearly 300 other sessions to hang! Not sure if this session itself got stuck due to some other activity - since it is all past now , how do we go about finding that out , I mean what in AWR can help to figure that out?
AWR will not help with the lock, but it will show you what other processes were going on that time. Perhaps one of them was slowing down or blocking your job. Check from the AWR report if you see anyhting that was not supposed to run or took unusually long.
Unfortunately if you don't have a logging process in the procedure called by your Scheduler job, it will be hard to get more information about the problem.