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  1. #1
    Join Date
    Feb 2008
    Posts
    15

    Unanswered: what is connection between shared memory and semaphore with sybase

    Is there any formula to calculate shared memory will setting in /etc/system.
    What is connection between semaphore with sybase.
    how much value we can set in /etc/system in place of shmmax.

  2. #2
    Join Date
    Sep 2003
    Location
    Switzerland
    Posts
    443
    Quote Originally Posted by jayantpathak
    Is there any formula to calculate shared memory will setting in /etc/system.
    What is connection between semaphore with sybase.
    how much value we can set in /etc/system in place of shmmax.

    Semaphore is the actual memory used by the Sybsae instance
    Shared Memory is the maximum memory all semaphores can use.

    ipcs -m (short display), ipcs -a (full display) show sthis.

    Ideally if its a box which is only used by Sybase, you can set it to the max possible leaving some for the O/S ofcourse.

    prtconf | grep Mem - will show you the memory currently available.

    Leave 20% for O/S and allocate the rest for shmmax.

  3. #3
    Join Date
    Feb 2008
    Posts
    15

    Kindly help me

    Thanks,
    As per my understanding semaphore is a locking mechanism.
    When i start the server it will create one instance and that instance is taking some amount of memory to run and semaphore is setting a lock on that part of shared memory.

    As per above mail, If my shared memory is 10Gb and i start the server it took 7Gb memory to start that time it will create one sybase instance. At this time what will be the semaphore values.

    Kindly help me.

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