SHMADD

The SHMADD parameter specifies the size of each increment of shared memory that the database server dynamically adds to the virtual portion. Trade-offs are involved in determining the size of an increment. Adding shared memory consumes CPU cycles. The larger each increment, the fewer increments are required, but less memory is available for other processes. Adding large increments is generally preferred; but when memory is heavily loaded (the scan rate or paging-out rate is high), smaller increments allow better sharing of memory resources among competing programs.

The range of values for SHMADD is 1024 through 4294967296 kilobytes on a 64-bit database server and 1024 through 524,288 on a 32-bit database server. The following table contains recommendations for setting SHMADD according to the size of physical memory.

For details on configuring shared-memory segments, see Configuring UNIX Shared Memory. For information on the SHMADD and SHMMAX parameters, see the IBM Informix: Dynamic Server Administrator's Reference.