Log switch/checkpoint question...
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  1. #1
    Join Date
    Mar 2001
    Posts
    13
    Hi All,
    I was wondering how often should I have a log switch/checkpoint to occur and also how can I prolong the time between the log switches if I have to do so.

    Bond.

  2. #2
    Join Date
    Feb 2001
    Posts
    389
    This depends on two factores mainly:

    1) Do u see checkpoint not complete in alert files, that means checkpoint is happening very fast , increase the size of redo log files .
    If you see in v$sysstat, that background checkpoints completed do not match with background checkpoints started, tune your DBWR.

    2) How often you want checkpoint to occur, how large is your redo log file, how large is your db_block_buffers, depending on that you can tune your checkpoint.

  3. #3
    Join Date
    Mar 2000
    Location
    india
    Posts
    54
    Hi,
    You can set this with two parameters one is 1.LOG_CHECKPOINT_INTERVAL and 2.LOG_CHECKPOINT_TIMEOUT.
    Second one works depending on the number of seconds that u set to checkpoint to occur,u set this in the parameter file.

    First one specifies that many number of filled OS blocks to be written to the database

  4. #4
    Join Date
    Feb 2001
    Posts
    40
    Hi,
    I would like to point it out that as per Oracle Documentation The check point value should be such that it is larger than the largest redo log file. This is due to the fact that occuring of checkpoint will cause some performance problems. Frequent checkpoints reduce the performance of the database. So u should have the checkpoint interval as stated above.

    Karthi

  5. #5
    Join Date
    Mar 2001
    Posts
    13
    Thanks for your replies,

    Is there a time range that the logfiles should switch as recorded in the alert.log file. At the moment my database instance is switching logfiles every 3 minutes. Is that too frequent?

    Thanks,
    Bond.

  6. #6
    Join Date
    Jan 2001
    Posts
    126
    Hi,

    What is the size of the redo log and how many groups you have? Based on that we can suggest the new sizes.

    Besides this, are you having "Checkpoint not complete" message in alert log?

    Baliga

  7. #7
    Join Date
    Mar 2001
    Posts
    13
    Hey There,

    The size of my redo log is 1M and I have three groups of log files. I have seen that message "Checkpoint not complete" before in my alert log.

    Thanks,
    Bond.

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