Shared memory question - Suse

This is a discussion on Shared memory question - Suse ; We had a situation where we were unable to start some of our database applications due to the lack of shared memory - specifically SHMMNI identifiers. Our linux group increased SHMMNI and SHMMAX to where it could map up to ...

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  1. Shared memory question

    We had a situation where we were unable to start some of our database
    applications due to the lack of shared memory - specifically SHMMNI
    identifiers. Our linux group increased SHMMNI and SHMMAX to where it could
    map up to 90% of the available physical memory on the system - based on a
    web page article that they had gotten from IBM.

    Then databases started crashing randomly with "Unable to allocate memory"
    errors for processes that were logging into the database that should not
    have been using any new shared memory.

    So my question is can anyone direct me to a source that can explain how
    shared memory vs physical memory can affect the use of non-shared memory?
    In other words can allocating too much shared memory with the kernel
    parameters on a server restrict the amount of memory that is available for
    other use?

    The question pertains to Progress v10.1A with SuSe Linux 2.6.5-7.244-smp #1
    SMP Mon Dec 12 18:32:25 UTC 2005 x86_64 x86_64 x86_64 GNU/Linux.

    Thanks.






  2. Re: Shared memory question

    Yeti wrote:

    > We had a situation where we were unable to start some of our database
    > applications due to the lack of shared memory - specifically SHMMNI
    > identifiers. Our linux group increased SHMMNI and SHMMAX to where it
    > could map up to 90% of the available physical memory on the system - based
    > on a web page article that they had gotten from IBM.
    >
    > Then databases started crashing randomly with "Unable to allocate memory"
    > errors for processes that were logging into the database that should not
    > have been using any new shared memory.
    >
    > So my question is can anyone direct me to a source that can explain how
    > shared memory vs physical memory can affect the use of non-shared memory?
    > In other words can allocating too much shared memory with the kernel
    > parameters on a server restrict the amount of memory that is available for
    > other use?
    >
    > The question pertains to Progress v10.1A with SuSe Linux 2.6.5-7.244-smp
    > #1 SMP Mon Dec 12 18:32:25 UTC 2005 x86_64 x86_64 x86_64 GNU/Linux.
    >
    > Thanks.


    How much physical memory do you have ? I've done what you are doing for an
    Oracle database keeping in mind what my 'system' requires. If you don't
    have much physical ram this can/will be a problem If on the other hand you
    have a lot of ram you may not want to assign too much to your application.

    You'll need to provide us with the actual amount of ram on your system.


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