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What useful information can I get from ASH report which I cannot get from AWR report? What are the common scenarios in which its better to get information from ASH than from AWR?

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  • For example you might help you tell "What happend just before tha database crashed?"
    – ibre5041
    Commented Feb 14, 2014 at 12:23
  • You might find this site kylehailey.com/ash-masters of use. HTH, Paul...
    – Vérace
    Commented Feb 14, 2014 at 22:27
  • @Ivan, yes that is a valid usecase but rare.
    – Deven
    Commented Feb 17, 2014 at 6:14

2 Answers 2

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AWR(Automatic Workload Repository Reports) takes snapshots of the database in specified intervals(one hour is default) and stores that data for later analysis. For example continuous improvement of the database work.

ASH(Active Session History) has information about current active sessions, and it gather data every second. If you are experiencing sudden database issues, you should use ASH.

More on this subject http://docs.oracle.com/cd/E11882_01/server.112/e16638/autostat.htm#PFGRF94186

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AWR report is averages which are misleading. ASH report gives much more precise information. For example the last section gives a breakdown of activity by time. ASH report gives the most important breakdown of TOP SQL and SESSIONS because the top list is ranked by activity in the database unlike AWR which ranks things on statistics like most reads, most CPU etc. I/O reads for example can be quite different if they are taking 0.1ms vs 100ms. ASH report will make it easy to see the difference

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