Job Setup

By using job setup you can cause JES3 to:

Reserve all devices needed by a job before the job executes
Mount all volumes needed by the job before the job executes

Thus, after the job starts to execute, it does not have to wait between job steps to have a device allocated or a volume mounted.

There are exceptions to the previous statements, however. The exceptions occur for:

Deferred volume mounting
Dynamic allocation
The mounting of other than the first volume of a multivolume data set on the same device.

For a multivolume data set, if the unit count and the volume count are unequal (unit count and volume count are DD statement subparameters), JES3 mounts the number of volumes specified as the unit count. Thereafter, MVS™ mounts subsequent volumes as they are needed.

When job setup is used, devices, volumes, and data sets are available for use by other jobs as soon as the DD statement is deallocated in the last step using the resource. Disadvantages of job setup are inefficient device usage and reserving devices for a job during steps when they are not used.

Job setup is used when SETUP=JOB is specified on a //*MAIN control statement for the job. If the SETUP parameter is not specified on the //*MAIN statement, then job setup is used only when specified (or assumed by default) on the STANDARDS initialization statement.