System tailoring

System tailoring is the overall process by which an installation selects its operating system. The process consists of the specification of system options through these mechanisms:
  • MVS™ hardware configuration definition (HCD), which is described in MVS hardware configuration definition.
  • Initialization-time selections which appear in the topic System tailoring at initialization time.
  • Implicit system parameters which appear in the topic Implicit system parameters.
  • After IPL, system tailoring through operator commands. One example of a command that will perform a system tailoring function is the SETPROG command (for example, SETPROG LPA,ADD). You get the same result whether you activate a function by issuing a SETPROG command or by activating the PROGxx parmlib member.

    For more information about how to use commands to start, load, initialize, and control your system, see z/OS MVS System Commands.

Note: Many system options have defaults. The IBM® defaults for some of these options might change in a future release. If you want to continue using the current default, set the default value that you want.

An installation can identify one or more active instances of the operating system. For example, the installation might choose to identify a specific instance to be used only during off-shift hours.

To identify an instance of the operating system, the installation assigns a unique 16-character EBCDIC identifier by using the AMASPZAP program immediately after system initialization, or by creating an alternate nucleus. For more information about AMASPZAP, see z/OS MVS Diagnosis: Tools and Service Aids. For more information about creating an alternate nucleus, see Specifying an alternate nucleus.