The system option MEMSIZE sets a limit on the amount of memory that the SAS System uses. If you do not specify a value for this option, then the SAS System sets a default memory limit. Your operating environment determines the actual size of the default memory limit set by the SAS System, which is sufficient for many applications. However, the solution of many realistic optimization problems can require more memory than the default. It is therefore recommended that the memory limit be increased above the default when you are solving optimization problems. This reduces the chance of a procedure failing because of an out-of-memory error.

Note: The MEMSIZE system option is not available in some operating environments. See the documentation for your operating environment for more information.

You can specify -MEMSIZE 0 to indicate that all available memory can be used, but use this setting with caution. In most operating environments, it is better to specify an adequate amount of memory than to specify -MEMSIZE 0. For example, if you are running PROC OPTLP to solve LP problems with only a few hundred thousand variables and constraints, -MEMSIZE 500M might be sufficient to enable the procedure to run without an out-of-memory error. When a problem has millions of variables, -MEMSIZE 2G or higher might be needed. These are rules of thumb; problems with atypical structure, density, or other characteristics can increase the optimizer’s memory requirements.

No matter how much memory is installed, 32-bit Windows operating systems permit the SAS System to use at most 4 gigabytes of memory. This memory limit might be lower, depending on which version of Windows you are running. The limit is enforced by the Windows operating system, not the SAS System.

You can specify the MEMSIZE option at system invocation, on the SAS command line, or in a configuration file. The syntax is described in the SAS Companion book for your operating environment.

To report a procedure’s memory consumption, you can use the FULLSTIMER option. The syntax is described in the SAS Companion book for your operating environment.