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.
• 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.
• 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.