The REALMEMSIZE system
option sets a recommended upper limit on real memory for procedures
that can use both real memory and utility disk space, such as PROC
SUMMARY and PROC SORT. This upper limit helps to avoid virtual memory
thrashing.
The REALMEMSIZE option
should never be set above the amount of real memory. If the amount
of real memory is insufficient for a job to run, then setting the
MEMSIZE option above the amount of real memory might enable the job
to run using a combination of real and virtual memory.