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  1. #1
    Join Date
    Aug 2008
    Location
    Toronto, Canada
    Posts
    2,367

    Unanswered: swap requirements for DB2 on Linux

    How much swap space do you allocate on Linux?

    "IBM InfoSphere Balanced Warehouse D5100: Design and Implementation Guide", if I'm reading it correctly, still suggests 1:1 (32GB of swap for 32GB of RAM). In addition, the following is recommended:

    " The file-system cache-related configuration parameters can be found in
    the /proc/sys/vm file. The recommended values for the file-system caching
    parameters are as follows:
    v swappiness: 0
    v dirty_ratio: 10
    v dirty_background_ratio: 5 "
    Last edited by db2girl; 11-16-10 at 23:04.

  2. #2
    Join Date
    Jan 2010
    Posts
    335
    Hi Bella,

    we usally don't use a 1:1. Mostly we use 1:8 on Linux. Mostly we have 2 - 4 GB Swap per Server. Even on Systems with 64 GB RAM and we never ran into issues.

    Windows requires at least a 1:1 ratio for Pagefile.

  3. #3
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    I agree with nvk@vhv. The 1:1 was required a long time ago for AIX systems (and maybe Linux) when max system memory was typcially much smaller.

    We also have used these with sucesss on all our OLTP systems:

    - swappiness: 0
    - dirty_ratio: 10
    - dirty_background_ratio: 5

    Linux tends to do too much swapping for file system cache without these.
    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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