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  1. #1
    Join Date
    Oct 2004

    Unanswered: Impact of Running EventMonitors

    I was wondering if there is any negative impact on the DB if we are running the eventmonitors continuously.

    We have setup the eventmonitors to run everyhour during peak business hours which collects all the sqls that were being processed by the DB. The idea had been to collect top rated sqls.

    Till now we didn't encounter any problems. But now we have a new database on the same server under the same instance and I have to enable the eventmonitors for collecting sql statements. I was worried about any negative impacts because of this. We are using "NONBLOCKED" evmon type and collects the information into a file.

    Please advice.


    - Raja

  2. #2
    Join Date
    Jul 2005
    Irvine, CA

    As you have now experienced, yes... In general, event monitors should only be run on a production systems as a last resort. An exception can be made for the deadlock monitor on V8. There are other exceptions, but they are on a case by case basis.

    This is one selling point that Oracle people love to bring up. The event monitor is one of the weak points of DB2 in my opinion. I've had it slow my dev and QA systems to a crawl during tests. You have to be very careful what you monitor, how much you monitor, and when.

    Unless you really need all SQL, a snapshot is usually enough for a decent picture of what is going on.

    -- Steve

  3. #3
    Join Date
    Aug 2001
    IIRC, I have heard that the impact is in the order of 2-5% depending on your workload .. Do not quote me on this, though ...

    the impact is much higher if you are writing monitor output to a table especially in a high transaction environment ...

    If you are writing to a file, make sure the IO of the event monitor file does not impact the IO of the database.. I mean at the IO System level ..

    Writing to a pipe may decrease the impact though you may be loosing a bit more monitor information than you do now ..



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