Specifying an Initialization Routine

You can optionally specify the name of your subsystem initialization routine when you define your subsystem. See Defining Your Subsystem for the list of ways that subsystems are defined to MVS™. If the functions the subsystem supplies might be needed during the IPL process, define your initialization routine in IEFSSNxx. In this case, the initialization routine handles all the preparation to ensure the subsystem is active.

To take advantage of running subsystem initializations in parallel, the IEFSSNxx parmlib member needs to be updated to include the BEGINPARALLEL keyword.

Note: All initialization routines specified before the BEGINPARALLEL keyword are invoked serially. All initialization routines specified after the BEGINPARALLEL keyword are invoked in parallel.

For IBM® products or a vendor-supplied subsystem, check the product's installation or configuration documentation to determine the placement of the BEGINPARALLEL keyword.