Log Buffer Size
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  1. #1
    Join Date
    Sep 2006
    Posts
    114

    Log Buffer Size

    i execute the following script
    SQL> @c:\sga_statistics.sql;

    PL/SQL procedure successfully completed.

    SQL> set serveroutput on;
    SQL> /
    > SGA CACHE STATISTICS
    > ********************
    > SQL Cache Hit rate = 99.24
    > Dict Cache Hit rate = 99.67
    > Buffer Cache Hit rate = 99.88
    > Redo Log space requests = 1440
    >
    > INIT.ORA SETTING
    > ****************
    > Shared Pool Size = 52428800 Bytes
    > DB Block Buffer = 32768 Blocks
    > Log Buffer = 20971520 Bytes
    >
    *** HINT: Log Buffer value is rather low!

    should i have to increase the size of log_buffer Because Redo Log space requests = 1440 is high?
    What u'll suggest Sir?
    thanx in advance

  2. #2
    Join Date
    Apr 2001
    Location
    Bangalore, India
    Posts
    727
    Your log buffer is too big. What is your redo log file size? "Redo Log space requests" shows the number of times a user process wait for a redo log file not for buffer.
    Last edited by Thomasps; 10-12-2006 at 05:35 AM.
    Thomas Saviour(royxavier@yahoo.com)
    Technical Lead (Databases)
    Thomson Reuters (Markets)

    http://ora600tom.wordpress.com/

  3. #3
    Join Date
    Sep 2006
    Posts
    114
    Quote Originally Posted by Thomasps
    Your log buffer is too big. What is your redo log file size? "Redo Log space requests" shows the number of times a user process wait for a redo log file not for buffer.
    we are having 3 redo log file of 1M
    should i increase size to 20m and add 1 more redo file?

  4. #4
    Join Date
    Oct 2006
    Location
    Mumbai
    Posts
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    Hi,

    I think increasing Redo Log size and Decreasing Log Buffer size might just help you.

    Your Log_buffer is too big

  5. #5
    Join Date
    Sep 2002
    Location
    England
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    7,333
    1M? are you serious??

  6. #6
    Join Date
    Apr 2001
    Location
    Bangalore, India
    Posts
    727
    20MB Log buffer and 1MB Redo log file.. Funny..! And that is the origion of your problem.

    Make 3 - 5 MB Log buffer and 25MB Log file atleast - Again depends on your Redo generation.
    Thomas Saviour(royxavier@yahoo.com)
    Technical Lead (Databases)
    Thomson Reuters (Markets)

    http://ora600tom.wordpress.com/

  7. #7
    Join Date
    Oct 2006
    Location
    Mumbai
    Posts
    184
    Dear Thomas,

    What is advisable size of REdo Log file, if Redo generation for the day is around 15 for 100MB size.

  8. #8
    Join Date
    Jun 2006
    Posts
    259
    Quote Originally Posted by pareshjavkar
    Dear Thomas,

    What is advisable size of REdo Log file, if Redo generation for the day is around 15 for 100MB size.
    I'd leave your log file alone at 100mb... If the db is generating more than 1 archive file per say 10 - 20 minutes.. then its time to increase the size.

  9. #9
    Join Date
    Mar 2002
    Location
    Mesa, Arizona
    Posts
    1,204
    Quote Originally Posted by ixion
    I'd leave your log file alone at 100mb... If the db is generating more than 1 archive file per say 10 - 20 minutes.. then its time to increase the size.
    Not picking on you, but I'm genuinely curious, is the 10-20 minute window for reasonable recovery .. Ex. "can't afford to loose up to 20 minutes of transactions"?

    What are the ramifications of time based vs. size based logging?

    I've heard that the redo should be larger for RAC. Is that true?

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

  10. #10
    Join Date
    Jun 2006
    Posts
    259
    Quote Originally Posted by Thomasps
    20MB Log buffer and 1MB Redo log file.. Funny..! And that is the origion of your problem.

    Make 3 - 5 MB Log buffer and 25MB Log file atleast - Again depends on your Redo generation.
    Log buffer is still too big even at 3 MB...

    Try starting out at 512K for you log buffer....

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