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  1. #1
    Join Date
    Sep 2009
    Posts
    66

    Unanswered: LOB - no file system caching

    LOB does not use DB2 buffer pool. Where is it cached if a table space is created with NO FILE SYSTEM CACHING on DB2 9.5.5 for Linux?

  2. #2
    Join Date
    Jan 2009
    Location
    Zoetermeer, Holland
    Posts
    746
    Nowhere, like you specified

  3. #3
    Join Date
    Sep 2009
    Posts
    66
    How and where DB2 updates LOB data if it's cached nowhere?

  4. #4
    Join Date
    Jan 2007
    Location
    Jena, Germany
    Posts
    2,721
    The data is stored on disk. So it is updated there.

    Caching is a mechanism to speed up the access to some data. It is a different concept than data modifications.
    Knut Stolze
    IBM DB2 Analytics Accelerator
    IBM Germany Research & Development

  5. #5
    Join Date
    Sep 2009
    Posts
    66
    Can DB2 skip caching regular data in the buffer pool and update it directly on disk?

  6. #6
    Join Date
    Jan 2007
    Location
    Jena, Germany
    Posts
    2,721
    What has a buffer pool to do with updating data? You open a file and write to it -> you changed the data in the file. The buffer pool in a database system and the associated page flushers/prefetchers are just there to do memory operations instead of read/write in order to improve performance.
    Knut Stolze
    IBM DB2 Analytics Accelerator
    IBM Germany Research & Development

  7. #7
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    Quote Originally Posted by L_DBA_L View Post
    Can DB2 skip caching regular data in the buffer pool and update it directly on disk?
    No, all pages (except for LOB's, etc.) are processed in the bufferpools.
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

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