Re: High Number of undo writes

  • From: Purav Chovatia <puravc@xxxxxxxxx>
  • To: Subodh Deshpande <deshpande.subodh@xxxxxxxxx>
  • Date: Mon, 21 May 2012 13:49:18 +0530

So finally to confirm that it was the SGA values and nothing else, I set
the values same as were set in the 10.2.0.5 env. in which we were seeing a
huge difference (high no. of undo writes to disk). I was expecting to again
see a huge difference (high undo writes to disk). But surprisingly I did
not see any difference appearing to mean that the problem was version
difference and not SGA difference. I am lost!!
Also, in this case we had a test and report where undo writes were
substantially less otherwise somebody who sees the test and report with
high undo writes would take it as correct because there are no errors, no
change of plan, the workload is exactly same and works fine without any
issues, etc. So the question arises - how to verify whether such internal
statistics (no. of undo writes to disk) are appropriate/optimal or no?
Because the difference between 2 was huge - IO statistics were very
different and it could have lead to substantial over sizing!

Regards


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