Results 1 to 5 of 5
  1. #1
    Join Date
    Nov 2003
    Location
    Portland, OR
    Posts
    8

    Question Unanswered: Buffer Cache Size

    Hello,
    I'm working with a database that has a buffer cache size of about 13mb, and the hit ratio is disgusting 50%. Users have complained of poor performce, and the buffer cache his ratio was one of the first things I noticed. So, I have the following questions:
    -Is 13mb way too small for a buffer cache size?
    -Is the poor buffer cache hit ratio likely to be something that might be causing the poor performance users are complaining about?
    -Is there any thing else I should be considering?

    Thanks.

  2. #2
    Join Date
    Sep 2003
    Location
    Columbia, MD USA
    Posts
    95
    13MB is a bit small in my opinion, but it really depends on the size of your database and the size of the most commonly used objects.

    There are too many factors that affect performance to say what your problem is without knowing more details, like size of db, what type of application, servers specs, etc..
    drew
    ------------------
    http://wjtechnologies.com

  3. #3
    Join Date
    Nov 2003
    Location
    Bangalore, INDIA
    Posts
    333

    Thumbs up Re: Buffer Cache Size

    Hi,
    13mb is really small. Try increasing the buffer cache size. Definitely poor buffer cache hit ratio affects the performance drastically.
    SATHISH .

  4. #4
    Join Date
    Sep 2003
    Location
    Columbia, MD USA
    Posts
    95
    I agree about the hit ratio... (forgot to put that in there)

    I would look at that first, but you might find that once you increase the buffer cache you've run into another bottleneck.

    If you post up some more details everyone might be able to help a little more.

    Is the buffer cache that low for a reason? like not enough memory in the server?
    drew
    ------------------
    http://wjtechnologies.com

  5. #5
    Join Date
    Sep 2003
    Location
    Milan, Italy
    Posts
    130

    Re: Buffer Cache Size

    Originally posted by Deren
    Hello,
    I'm working with a database that has a buffer cache size of about 13mb, and the hit ratio is disgusting 50%. Users have complained of poor performce, and the buffer cache his ratio was one of the first things I noticed. So, I have the following questions:
    -Is 13mb way too small for a buffer cache size?
    -Is the poor buffer cache hit ratio likely to be something that might be causing the poor performance users are complaining about?
    -Is there any thing else I should be considering?

    Thanks.
    13Mb may be small or huge depending on the application, even if, in these days of cheap RAM, it's normally considered small. You can up the DB_BLOCK_BUFFERS parameter to increase it - check the performance afterward and see if it has improved.

    Forget the buffer cache hit ratio - a perfectly optimized system can have a ratio of 1% of 99.99% - it doesn't tell you nothing (contrary to common opinion) alone.

    There are a lot of things that can harm a database - missing indexes, too many indexes, no statistics collected, statistics collected for an application that doesn't like them ... unfortunately you can't diagnose a problem without knowing how the database works, and a lot of experience.

    Of course, with some more details, you could have some advice from me/us...

    bye
    Al

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •