z/OS MVS JCL Reference
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Running a started task under the master subsystem

z/OS MVS JCL Reference

These additional considerations apply to a started task that runs under the master subsystem:
  • Any started task that can operate under the master subsystem can also run under the primary JES subsystem.
  • A started task running under the master subsystem (SUB=MSTR) may choose to use JES services. To do so, the task must issue a Request Job ID call to the JES. (See z/OS MVS Using the Subsystem Interface for additional information about the Request Job ID call.)
  • The started task may include JES statements and commands with the // COMMAND statement. Note, however, that if JES is not running, the system may queue or purge these statements.
  • The JCL may not include a JCLLIB statement.
  • The JCL may include PROC and PEND statements if the JCL is a procedure, but not if it is a job.
  • The started task may not have SYSIN data sets.
  • Start of change The system will initially allocate only data sets that are cataloged in the master catalog or a user catalog. Catalogs must reside on online volumes. End of change
  • You may dynamically allocate data sets that are not cataloged in the master catalog to a task running under the master subsystem during execution.
  • You may dynamically allocate SYSOUT data sets after successfully completing a Request Job ID SSI call.
  • JES exits do not get control during startup processing of a started task. If, however, the started task issues a Request Job ID SSI call, JES exits will get control for the minimal JCL used to construct the JES job structure.
  • SMF exits, such as IEFUJV, get control with the subsystem shown as SYS.
  • SRM determines performance characteristics based on the master subsystem.
  • You may not specify JES3-managed devices in the procedure; JES3 cannot manage devices for tasks that run under the master subsystem.
  • You must code a TIME= value on the EXEC statement of the procedure (such as TIME=NOLIMIT), or else specify the program as a system task in the program properties table (PPT). Otherwise, the task will end abnormally with a time-out condition.
  • You must specify the region size that will be used if REGION is not specified in the JCL.

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