Decision 7: Whether and where to use variables

Variables allow systems to share parameter definitions while retaining unique values in those definitions. Variables can take on different values, based on the input to the program. When you specify a variable in a shared parameter definition, the variable acts as a placeholder. Each system that shares the definition replaces the system variable with a unique value during initialization.

If you use variables, the components inherit the system values of the system on which they are started (the host z/OS® system). These system-specific values are then automatically loaded into temporary data sets that exist only while the component runs. The result is that the software runs correctly by using the system-specific parameter values for the host z/OS system.

Using variable support includes the following benefits:
  • You can deploy the same software unit, consisting of any or all TMS:Engine-based products, on any system without modification. LPAR-specific values are automatically resolved and substituted at product startup.
  • The number of unique runtime environments required is smaller (although unique physical data sets must still exist.) This feature saves storage space, CPU, and labor.
  • The same started task JCL and the same VTAM® node can be used on any system without modification.
  • You can choose to use a single VTAM major node in place of the individual product major nodes. When generated, a single VTAM major node contains all VTAM applids for all TMS:Engine-based products you have configured in the runtime environment.
Tips:
  • You cannot use variables in the runtime environment of a high-availability hub. (Because the high-availability hub can be started on any LPAR with DVIPA, parameters such as the monitoring server node ID, name, and VTAM major node must be set to static values.
  • Product started tasks contain a preprocessing step that resolves all variable specifications in the product parameter members.
  • If you enable variable support, product parameter members contain many variables whose values are resolved during startup of the started task.

See the z/OS MVS™ Initialization and Tuning Reference (SA22-7592) for basic information on system variables.

See Variables in PARMGEN configuration for more information about using variables.