Using exit routines to limit region size

Two MVS installation exits are available to override the region values that JES passes to MVS. The exit routines are called IEFUSI and IEALIMIT and are described in detail in z/OS MVS Installation Exits.

The installation can use either IEFUSI or IEALIMIT to change the job's limit for the region size below 16 megabytes of virtual storage. However, to change the limit for the region size above 16 megabytes, the installation must code the IEFUSI installation exit.

If your installation does not supply an IEFUSI exit routine, the system uses the default values in the IBM-supplied IEALIMIT exit routine to determine region size. To determine region limit, the system adds 64K to the default region size.

Region and MEMLIMIT values and limits set by the IEFUSI exit will not be honored for programs with the NOHONORIEFUSIREGION program property table (PPT) attribute specified. The NOHONORIEFUSIREGION PPT attribute can be specified in the SCHEDxx member of SYS1.PARMLIB, or as an IBM® supplied PPT default. This PPT attribute is used to bypass IEFUSI region controls for specific programs that require a larger than normal region in order to successfully execute.