Partial workaround for increased redo generation on EM12cR2 repository database after upgrade from R1

Another followup to my previous posts on increased redo logging on the repository database after upgrading to EM12cR2.

On the OTN Forum thread, slohit posted a suggestion with a way to reduce the frequency of job dispatcher runs:

To reduce the frequency of inserts, it would be better to slow down the frequency of the dispatcher. This is OK only if you are fine with a lower response time between steps for your jobs. If it is only a few jobs/job steps scheduled to run together, this is all right

emctl set property -name oracle.sysman.core.jobs.minDispatcherSleepInterval -value 0.5
emctl set property -name oracle.sysman.core.jobs.linearBackoff -value 0.5

By making this change, followed by a bounce of the OMS, the redo generation on my repository database decreased by about 50%. It’s still 200-300% more than before the upgrade, but it’s quite an improvement. The EM_JOB_METRICS table now only receives about 20 inserts per second compared to 60. My 13GB repository database should now only produce about 5GB of redo per day instead of 10GB.

Prior to the change, emctl get property reported these property values as null so presumably the OMS was working with whatever the built-in default values were.

In my case, a delay between job steps is a tradeoff that I can tolerate. This OMS runs simple database backups, SQL and RMAN scripts, so I do not have any time-critical multi-step jobs that could be negatively impacted by delayed response to completion of individual job steps. Your mileage may vary.

Oracle Support is continuing to investigate this bug. At least one other poster on the forum has reported that they too are experiencing this issue so I’m looking forward to finding out if this change reduces their redo generation to an acceptable rate. That same poster also reports that they do not see the issue on a new install of EM12cR2, only on a system upgraded from R1. It’s not clear to me why an upgraded system would experience this when processing the raw metric data while a fresh install would not, nor is it clear how many upgraded systems are experiencing the issue. But at least we now have a partial workaround for bug 14726136.

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One thought on “Partial workaround for increased redo generation on EM12cR2 repository database after upgrade from R1

  1. Pingback: Final (!) update/fix for EM12c increased redo from EM_JOB_METRICS after upgrade to R2 (bug/patch 14726136) | Pardy DBA

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