Tuning Semaphore Parameters

Refer to the following guidelines if the default semaphore parameter values are too low to accommodate all Oracle processes.


Oracle recommends that you refer to the operating system documentation for more information about setting semaphore parameters.

  1. Calculate the minimum total semaphore requirements using the following formula:

    2 * sum (process parameters of all database instances on the system) + overhead for background processes + system and other application requirements

  2. Set semmns (total semaphores systemwide) to this total.

  3. Set semmsl (semaphores for each set) to 250.

  4. Set semmni (total semaphores sets) to semmns divided by semmsl, rounded up to the nearest multiple of 1024.