System Options under UNIX

REALMEMSIZE System Option: UNIX

Specifies the amount of real (physical) memory SAS can expect to allocate.

Default:	0
Valid in:	configuration file, SAS invocation, SASV9_OPTIONS environment variable
Category:	System administration: Memory
PROC OPTIONS GROUP=	MEMORY
UNIX specifics:	valid values

Syntax
Details
Comparisons
See Also

Syntax

-REALMEMSIZE n | nK | nM | nG | hexX | MIN | MAX

n | nK | nM | nG: specifies the amount of memory to reserve in multiples of 1 (bytes); 1,024 (kilobytes); 1,048,576 (megabytes), or 1,073,741,824 (gigabytes). The value of n can be a decimal value. For example, a value of 8 specifies 8 bytes, a value of .782k specifies 801 bytes, and a value of 3m specifies 3,145,728 bytes.
hexX: specifies the amount of memory as a hexadecimal value. You must specify the value beginning with a number (0-9), followed by hexadecimal characters (0-9, A-F), and then followed by an X. For example, the value 2dx sets the amount of memory to 45 bytes.
MIN: specifies a value of 0, which indicates that the memory usage is determined by SAS when SAS starts.
MAX: specifies to set the memory size to the largest permissible value. This value depends on the system limit.

Details

The REALMEMSIZE system option sets a recommended upper limit on working memory for procedures that can use both memory and utility disk space, such as PROC SUMMARY and PROC SORT, so that they can avoid virtual memory thrashing.

The REALMEMSIZE option should never be set beyond the amount of real memory. If the amount of real memory is insufficient for a job to run, then setting the MEMSIZE option beyond the real memory might enable the job to run using a combination of real and virtual memory.

Comparisons

Some SAS procedures use the REALMEMSIZE system option to specify how much real memory the procedure can allocate and use without inducing excessive page swapping. By contrast, the MEMSIZE system option places a limit on the total amount of virtual memory that SAS dynamically allocates at any time. This virtual memory is supported by a combination of real memory and paging space.

The operating environment begins paging when the amount of virtual memory that is required exceeds the real memory that is available. To prevent paging and the associated performance problems, the REALMEMSIZE and MEMSIZE system options should be set to a subset of real memory.