Controlling system definition processing

When planning a change to system definition, you usually have to coordinate a series of macro changes. The IMS system definition stage 1 input is suggested as a point of control.

Review changes to the macros for the accuracy of the parameter values and add adequate explanation of how the value was derived. You should have a control document that records the nature of the proposed change, the reason for it, and suitable authorization. You can then complete the record by entering the action taken, or planned, for each item.

You must also coordinate the timing of the system definition stage 2 processing. The new version of the control program, with any required JCL changes, must be tied to an operational cutover.

Re-specifying a parameter on one or more macro statements does not require a full system definition or the processing of a complete stage 2 jobstream. You can make many tuning changes by overriding parameter values with others specified in the JCL statements. You can delay making the new values a permanent part of the control program until a more extensive change occurs in the macro content. Consider that all such overrides need to be coordinated with PROCLIB contents and operator instructions.