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Thread: Init.ora Parameters and Unix Kernel

  1. #1
    Expert Oracle Administrator
    Join Date
    Oct 2011
    Delhi, India, India

    Init.ora Parameters and Unix Kernel

    Relationship Between Common Init.ora Parameters and Unix Kernel Parameters


    The following table documents Unix kernel parameters that should be
    monitored and possibly increased after changes are made to the related
    init.ora parameter. Please check with your Operating System documentation
    for specific details on the parameter changes.

    Init.ora Parameter Unix Kernel Parameter
    ------------------------- -------------------------
    sga_max_size - shmmax
    db_cache_size - shmmax
    db_files (maxdatafiles) - nfile, maxfiles
    large_pool_size - shmmax
    log_buffer - shmmax
    processes - nproc, semmsl, semmns
    shared_pool_size - shmmax

    Common Unix Kernel Parameter Definitions

    The following Kernel Parameters tend to be generic across most Unix
    platforms. However, their names may be different on your platform.
    Consult your Installation and Configuration Guide (ICG) for the exact

    maxfiles - Soft file limit per process.
    maxuprc - Maximum number of simultaneous user processes per userid.
    nfile - Maximum number of simultaneously open files systemwide at any given time.
    nproc - Maximum number of processes that can exist simultaneously in the system.
    shmmax - The maximum size(in bytes) of a single shared memory segment.
    shmmin - The minimum size(in bytes) of a single shared memory segment.
    shmmni - The number of shared memory identifiers.
    shmseg - The maximum number of shared memory segments that can be attached by a process.
    semmns - The number of semaphores in the system.
    semmni - The number of semaphore set identifiers in the system; determines the
    number of semaphore sets that can be created at any one time.
    semmsl - The maximum number of sempahores that can be in one semaphore set. It
    should be same size as maximum number of Oracle processes.


    Note:1010913.6 - Unix Configuration Parameters: Where to set Semaphores and Shared Memory
    Note:1008866.6 - How to determine SGA Size (7.x, 8.0, 8i)
    Note:1012819.6 - Operation System Tuning issues on Unix
    Note:1011658.6 - Shared Memory requirements on Unix
    Last edited by Hemant; 11-04-2011 at 05:57 PM.

  2. #2
    Expert Oracle Administrator
    Join Date
    Oct 2011
    New Delhi, India
    Thanks for this very helpful post Amit , to keep in mind the checks that need to be done on the OS side , prior to modifications to the init parameters.

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