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Thread: Cache table

  1. #1
    Join Date
    Sep 2002
    Posts
    456

    Post Unanswered: Cache table

    O/S : AIX 5.x
    DB : UDB V7.2

    Hi: Is there a way to know if a request to select data from table is being picked up from cache or from disk-cache combination. I am in the process of fine tunning some of our database systems and wondering if I can found out this information somewhere i.e. through a monitor or snapshot.

    Thanks in advance.

    dollar

  2. #2
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650

    Re: Cache table

    I think you can do, a sort of but .....

    You can look at bufferpool logical/physical reads in the tablespace snapshot .... This may give you an idea ...

    But in realtime, the bufferpool may be used by other tables in the tablespace and your table may be flushed out ... If you want this table in the bufferpool always, put this table in an individual tablespace and a bufferpool exclusively for this tablespace ...



    Cheers
    Sathyaram


    Originally posted by dollar489
    O/S : AIX 5.x
    DB : UDB V7.2

    Hi: Is there a way to know if a request to select data from table is being picked up from cache or from disk-cache combination. I am in the process of fine tunning some of our database systems and wondering if I can found out this information somewhere i.e. through a monitor or snapshot.

    Thanks in advance.

    dollar
    Visit the new-look IDUG Website , register to gain access to the excellent content.

  3. #3
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    First you need to set the bufferpool monitoring to "on" at the server. Be advised that this uses extra overhead, so set it to “off” on a production system after you are done.

    db2 update monitor switches using bufferpool on

    Then you can monitor the bufferpool usage with a monitor tool. I have been using the 3rd party monitor tool (free) provided at http://chuzhoi_files.tripod.com/ (as listed in the Useful DB2 Stuff).

    When using the 3rd party tool above, Select Bufferpools from the Monitor pull down menu. You can hit the refresh after each SQL query that is run, or use auto-refresh at the selected interval.

    Keep in mind that in DB2 terminology, the data and indexes are stored in "bufferpools." Cache is storage used for all other things such as packages, catalog, etc.

    I sometimes use the “Lazy-DBA Monitor” when working on (or next to) the database server. I just watch the disk I/O light of the server.

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