The EXEC statement must contain a time limit of 1440 or the program must be defined as a system task in the program properties table (PPT) to ensure that the master scheduler does not time out. See the description of the SCHEDxx parmlib member in SCHEDxx (PPT, master trace table, and abend codes for automatic restart) for information about allowing your installation to specify programs in the PPT.
The master scheduler (IEEMB860) is defined in the PPT with several options; among them are SYST (system task) and NODSI (no data set integrity). SYST ensures that the master scheduler does not time out. NODSI means that the master scheduler JCL defined data sets are not enqueued or shared by MVS™. This keeps the master scheduler from having to deal with enqueue contention for data sets, such as SYS1.PARMLIB. It also means that it is possible to move members within the data set while the system is trying to read them. This can result in I/O errors. Any manipulation of the data sets defined to the master scheduler JCL should be done with extreme caution.
If you specify this DD statement and there are parmlib statements in the LOADxx member of SYS1.PARMLIB, IEFPARM is ignored, a warning message is issued and the LOADxx parmlib data sets are used. If the specified parmlib statements in LOADxx cannot be found, IEFPARM is ignored, a warning message is issued and the system uses SYS1.PARMLIB as the default. If there are no parmlib data sets specified in LOADxx, the system uses the parmlibs on the IEFPARM DD statement.
If you do not specify this DD statement, the system uses the parmlib data sets specified in the LOADxx member of SYS1.PARMLIB. If no parmlib data sets were specified in LOADxx, or if the specified parmlib data sets cannot be found, the system uses SYS1.PARMLIB as the default. If no SYS1.PARMLIB is cataloged, the system uses the SYS1.PARMLIB on the SYSRES volume.
See Sharing parmlib definitions for general information about defining and using system symbols in parmlib. See z/OS MVS JCL Reference for details about using system symbols in JCL.