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Thread: forcedirection for oracle

  1. #1
    Join Date
    Oct 2001
    Posts
    45

    forcedirectio for oracle

    Hi,
    According to Sun doc that forcedirectio will help impove oracle performance, but I want to know if Oracle recommends forcedirectio for its database? Why would lots of DBAs not use forcedirectio if it always means better performance? What could be the side effect of implementation forcedirection for Oracle datafiles? Can anybody here share your experience/knowledge of forcedirectio? Any comments are highly appreicated.

    Thanks in advance.
    Xiaomao
    Last edited by xiaomao; 04-13-2005 at 04:32 AM.

  2. #2
    Join Date
    Feb 2003
    Location
    Leeds, UK
    Posts
    367
    I believe forcedirectio is like direct io on vxfs filesystems e.g. bypasses the OS buffer cache. This is something you should test first, rather than putting directly into production. It is possible that it could make performance worse rather than better. If you have an physical problem already but most of your physical reads are actually from the OS buffer cache it is helping you along. Removing the cache will lead to more actual physical IO and if disk wait times are already a problem it could get worse.

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