REGION parameter

Parameter type

Keyword, optional

Purpose

Use the REGION parameter to specify the amount of central or virtual storage that the job requires. The system applies the value that you code on REGION to each step of the job.

Start of changeThe amount of storage that you request must be sufficient to accommodate the following:
  • Storage for all programs in each step to run in the limited storage areas.
  • All additional storage that the programs in each step request either directly or indirectly via a storage management environment such as Language Environment with GETMAIN, STORAGE, and CPOOL macro instructions.
  • Start of changeStorage for the programs in each step should be limited to leave enough unallocated storage for task initialization. If low private is allowed to restrict the required high private demand, system and other authorized programs will not function properly. See z/OS MVS Authorized Assembler Services Guide for more details.End of change
End of change

Start of changeThe REGION parameter is responsible for directly setting the region size thresholds for 24 and 31 bit low private. This parameter also indirectly sets the region limit thresholds for 24-bit (user region, low private) and 31-bit (extended user region, extended low private) memory. The region size provides an upper bound on the amount of memory that could be allocated on a single variable length STORAGE OBTAIN or GETMAIN request, based on the specified LENGTH and the amount of low private previously obtained. The REGION LIMIT provides an upper bound on all STORAGE OBTAIN or GETMAIN requests and should be greater than or equal to the region size. Assuming that neither SMFLIMxx nor system exits like IEFUSI change these values, this results in the following:End of change

Start of change
  • A value equal to 0K or 0M - gives the job step all the storage available below and above 16 megabytes. The resulting size of the region below and above 16 megabytes depends on system options and what system software is installed. When REGION=0K/0M is specified, the MEMLIMIT is set to NOLIMIT.
    Note: This might cause storage problems. See the Considerations When Using the REGION parameter information for more information.
  • A value greater than 0K or 0M and less than or equal to 16,384K or 16M - establishes the size of the private area below 16 megabytes. If the region size specified is not available below 16 megabytes, the job step abnormally ends with an ABEND822. The extended region size is the default value of 32 megabytes.
  • A value greater than 16,384K or 16M and less than or equal to 32,768K or 32M - gives the job step all the storage available below 16 megabytes. The resulting size of the region below 16 megabytes depends on system options and what system software is installed. The extended region size is the default value of 32 megabytes.
  • A value greater than 32,768K or 32M and less than or equal to 2,096,128K or 2047M - gives the job step all the storage available below 16 megabytes. The resulting size of the region below 16 megabytes depends on system options and what system software is installed. The extended region size is the specified value. If the region size specified is not available above 16 megabytes, the job step receives whatever storage is available above 16 megabytes, up to the requested amount, and the resulting size of the region above 16 megabytes depends on system options and what system software is installed.
End of change

References

For more information on address space size, see z/OS MVS Initialization and Tuning Guide, and "Resource Control of Address Space" in z/OS MVS JCL User's Guide. For more information on region size with checkpoint/restart jobs, see z/OS DFSMSdfp Checkpoint/Restart.