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Thread: SGA for standby

  1. #1
    Join Date
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    SGA for standby

    Is there a better SGA configuration for maximizing recovery performance on a standby database?

    *.sga_max_size=1048576000
    *.sga_target=1048576000

    Total System Global Area 1048576000 bytes
    Fixed Size 2089272 bytes
    Variable Size 419434184 bytes
    Database Buffers 616562688 bytes
    Redo Buffers 10489856 bytes

    Thanks in advance,
    Ken
    "I do not fear computers. I fear the lack of them." Isaac Asimov
    Oracle Scirpts DBA's need

  2. #2
    Join Date
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    Hi

    DId you discover actually SGA is the bottleneck in maximum performance mode are you behind a WAN or a LAN

    Did you finish tuning the NET8 related parameters ?

    have a look at MAA whitepapers specifically
    http://www.oracle.com/technology/dep...tPractices.pdf


    http://www.oracle.com/technology/dep...tPractices.pdf

    regards
    Hrishy
    Last edited by hrishy; 12-16-2008 at 02:13 AM.

  3. #3
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    Quote Originally Posted by hrishy
    DId you discover actually SGA is the bottleneck in maximum performance mode
    I have no reason to believe the current SGA configuration is underperforming. Just hoping to find some some silver bullet like "larger db block buffers speed up recovery"

    Quote Originally Posted by hrishy
    are you behind a WAN or a LAN
    I'm local at the DR site, so network is not an issue.

    Thanks,
    Ken
    "I do not fear computers. I fear the lack of them." Isaac Asimov
    Oracle Scirpts DBA's need

  4. #4
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    There are two things to consider when sizing the standby SGA. First, does a larger SGA help with applying logs? You have to think of what the SGA does and what applying logs really is. Applying logs is really a recovery. The database isn't open, there's no SQL being executed, and the changes are being done block by block.

    Second, is the SGA I have specified adequate in the case of a failover? This is a bigger consideration because you don't want a primary db with a 8GB SGA shipping logs to a Standby db that has a 1G SGA and it's failover time. Unless your automated failover scripts know to bump the SGA back up to 8g, your failover performance is going to be horrible (probably).

    Personally, I like to run my standby dbs with the same size as my primary unless the standby hardware is different. In that case, I'll run with the size SGA I want when/if I failover. I do, however, run with two different init.ora files depending on whether I am applying logs or acting as a failover db.

    YMMV
    Jeff Hunter

  5. #5
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    That all makes perfect sense in my world. Thank you!
    -Ken
    "I do not fear computers. I fear the lack of them." Isaac Asimov
    Oracle Scirpts DBA's need

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