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  1. #1
    Join Date
    Jan 2003

    Angry Unanswered: Why shmvirtsize increase so quickly

    informix server config 200M shmvirtsize and 100M shmadd,But we find everyday,It will increase a share memory segment(100M),any way can I find out why the shmvirtsize turn to large? what operation will cause this situation? Thanks

  2. #2
    Join Date
    Aug 2003

    I suggest that you increase SHMVIRTSIZE=300M, but SHMADD=32768.
    If the on-line allocate virtual segment, then increase SHMVIRTSIZE.
    Some of the causes is update statistics, oncheck of indices, orde by bigs.


  3. #3
    Join Date
    May 2004
    Virtual Seg holds memory for connections, SQL statement memory for prepares/stored procedures, active result sets - basically anything that is not a data row (which goes to the buffer segment). Memory leaks like new SQL cursors being created but never closed or a large number of users running programs with lots of sql and returned rows can typically flood the virtual segment. You can remove 'stale' chunks of used memory using the 'onmode -F' command which can reduce the used % of the segment but it causes a brief performance hit while the search for stale memory is completed.
    Keith Brownlow
    ServerMetrics DB Monitoring (

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