Estimating the size of the resident portion of shared memory

You can use formulas to estimate the size of the resident portion (in KB) of shared memory when you allocate operating-system shared memory.

The result of your calculations is an estimate that normally, slightly exceeds the actual memory that is used for the resident portion of shared memory.

The following estimate was calculated to determine the resident portion of shared memory on a 64-bit server. The sizes that are shown are subject to change, and the calculation is approximate.

To estimate the size of the resident portion of shared memory

  1. Calculate the values in the following formulas:
    locks_value = LOCKS * 136
    logbuff_value = LOGBUFF * 1024 * 3
    physbuff_value = PHYSBUFF * 1024 * 2
  2. Calculate the estimated size of the resident portion in KB, using the following formula:
    rsegsize = 1.02 * (locks_value + logbuff_value 
               + physbuff_value + 1,200,000) / 1024

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