How to determine how long dbms_job jobs take to execute?

Question

I have a number of dbms_Jobs (snapshot refresh jobs created automatically by creating the refresh groups) and I'm required to determine how long the jobs are running to verify some timelines. I was hoping it would be as easy as recording the last_date and next_date frequently and when there are changes, use the delta to determine (since the jobs are supposed to be scheduled from the completion of the previous job) but this doesn't appear to be working. I created a simple job that just sleeps for 15 seconds with an interval of 5 minutes, and (next_date - last_date) is always 5 minutes. What I would have expected was
Job starts at 00:00:00 (last_date)
Runs for 15 seconds, ends at 00:00:15
Scheduled out 5 minutes: 00:05:15 (next_date)
In that example next_date - last_date would be 5:15, and knowing the interval was 5 minutes I could determine it ran for 15 seconds.
In practice though the current next_date becomes the next last_date (as if the interval is being calculated when the job starts, not completes), so it always shows 5 minutes which is just the interval.
Short of not using the default jobs, and just submitting my own to do the refresh where I add some logic to record the duration, is there a good way to get this information? I'm using 10.2.0.4.
Thanks

Answer 1

Did you check out the TOTAL_TIME column of the DBA_JOBS view?
:p