Initializing MVS

An operator can specify certain system parameters during MVS™ initialization or you can specify system parameters in an MVS data set named SYS1.PARMLIB. The purpose of SYS1.PARMLIB is to provide many initialization parameters in a predefined form in a single data set, and thus minimize the need for operator entry of parameters during MVS initialization.

To use JES3 as the primary job entry subsystem, you must specify JES3 in member IEFSSNxx of SYS1.PARMLIB. Otherwise, MVS will default to IEFSSN00, which specifies JES2. You must also define all consoles in your installation in the CONSOLxx member of SYS1.PARMLIB to ensure console integrity. See z/OS MVS Initialization and Tuning Guide for information about how to use SYS1.PARMLIB.