Starting the APPC and ASCH Address Spaces

IBM® supplies procedures in SYS1.PROCLIB that support starting the APPC and APPC/MVS transaction scheduler (ASCH) address spaces with the START command. You can modify these procedures to meet your installation's data processing requirements; for example, you may use names other than APPC and ASCH for the started procedures or for the jobnames of the APPC and ASCH address spaces. If you do so, however, remember that you must use these different procedure names or jobnames, instead of "APPC" or "ASCH", on subsequent START and CANCEL commands. Renaming the address spaces might cause problems if APPC/MVS tries to automatically restart one of its address spaces; see Restarting APPC/MVS for more information about restart attempts.

The EXEC statements in the APPC and ASCH procedures shipped in SYS1.PROCLIB specify REGION=0K. If the installation does not modify the specified REGION=0K in an installation exit such as IEALIMIT or IEFUSI, the system gives the job step all the requested storage available below and above 16 megabytes. The resulting size of the region below and above 16 megabytes is unpredictable.

The IBM-supplied procedures specify REGION=0K because the APPC workload and configurations that each installation plans to run determine the amount of private storage that APPC requires. See Considering APPC/MVS Storage Requirements for information about APPC/MVS storage usage.

To limit the region size of APPC/MVS, modify the REGION=0K parameter on the EXEC statement in the APPC and ASCH procedures.

To start the APPC and ASCH address spaces for APPC/MVS, issue the START (S) command to initialize each address space as follows:

   START APPC,SUB=MSTR,APPC=xx
   START ASCH,SUB=MSTR,ASCH=xx

If you renamed the APPC or ASCH started procedures, specify the actual procedure name, instead of "APPC" or "ASCH" immediately after "START".

The xx represents the identifier for the parmlib member that contains initializing parameters. When no identifier is specified, the default for APPC is APPCPM00, and the default for ASCH is ASCHPM00. IBM does not supply default members with these names; however, sample APPCPMXX and ASCHPMXX members are in SYS1.SAMPLIB.

To specify more than one parmlib member after the START command, issue the commands as follows:

   START APPC,SUB=MSTR,APPC=(xx,yy,...)
   START ASCH,SUB=MSTR,ASCH=(xx,yy,...)

To start the APPC and ASCH address spaces automatically at IPL, an installation can add these START commands to the COMMNDxx member of the parmlib concatenation. The parmlib members used in the commands must be coded before the IPL.