Define and add secondary subsystems to MVS™ by defining the subsystems in the SYS1.PARMLIB member IEFSSNxx. These members contain lists of subsystems to be defined to MVS during master scheduler initialization. The SSN option can be specified when the system parameters are initialized or in IEASYSxx. (IEFSSN00 is reserved for IBM® use.) The syntax for the SSN option is as follows:

This is the recommended method for defining and modifying a secondary subsystem. See z/OS MVS Initialization and Tuning Guide for further information.