V$ROLLSTAT - some explanation needed please?
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Thread: V$ROLLSTAT - some explanation needed please?

  1. #1
    Join Date
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    Might sound straighforward but I just don't want to be misunderstanding this:

    V$ROLLSTAT - can you explain - in simple terms! - what the values of the columns: EXTENTS, WRITES, EXTENDS mean? And does the value of the CUREXT column indicate the current extent being used? (ie) if set to 10 and I have MAXEXTENTS of 500 for the RBS, then I have 490 1Mb extents free in the RBS?

    Also - What use will I have for knowing the Current Block (the value of CURBLK) being used?

    Thanks (and Merry Christmas)

  2. #2
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    V$ROLLSTAT is one of the most important view in Oracle, well, at least in my opinion.

    EXTENTS tells you how many extents you have now in the rollback segment

    WRITES is selfclear

    EXTENDS tells you how many times the RBS obtained an extent. Do you understand the difference between an EXTENT and EXTEND?

    I usually follow also the values of SHRINKS, XACTS and WAITS.

  3. #3
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    Trying to understand what's important - on a daily maintenence basis. What should I look out for? I understand a bit about EXTENDS (how many times the RBS has acquired a new extent) - When does this figure reset itself? Ever? What is it's significance?
    As for EXTENTS - is this the number of EXTENTS currently in use by the RBS (ie) All the others can be re-used?

    What is the significance of the SHRINKS, XACTS & WAITS figures that you rely on them so much?

    Many thanks

  4. #4
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    I suggest you buy a book about Oracle tuning or read on Metalink in detail about these things. I believe this is the proper way to learn them, not through Oracle forums on the Internet. I find this forum more useful for finding the answers to a specific difficult situation, not about basics.






  5. #5
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    Originally posted by JMac
    When does this figure reset itself? Ever? What is it's significance?

    This figure is reduced when a "SHRINK" happens. A shrink is determined by the OPTIMAL setting on your RBS.


    As for EXTENTS - is this the number of EXTENTS currently in use by the RBS (ie) All the others can be re-used?

    Yes, this is the number of extents currently in use. The free extents may be used by another RBS.


    What is the significance of the SHRINKS, XACTS & WAITS figures that you rely on them so much?
    The shrinks signifies the number of times your RBS shunk back to the OPTIMAL size. The thing to watch out for here is to make sure your shrinks and extends don't get too much activity. If they do, your rbs is probably sized improperly.

    XACTS is the number of transactions currently in that particular RBS. This number is useful if you want to see if your RBS is "in use" at the moment.

    WAITS is the number of waits that were experience in that RBS. High occurrances of this number may indicate RBS contention and that you need more RBS.

    Check out http://home.adelphia.net/~marist89/s...p_rollback.htm for a script that takes a snapshot of your rollback segments.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  6. #6
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    Oh, and you may want to check out http://otn.oracle.com/docs/products/...llbak.htm#1083 for the "exact" definitions of the columns.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

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