How to set the level of operator control

IMS is designed so processing is controlled by message traffic, which places control of the operation primarily in the hands of the master terminal operator. From an administration point of view, control of operations is far more than a structured use of IMS commands.

For a complex system such as IMS, you need to carefully match operational control to operator capability. You must decide whether an operator or an application administrator should have primary control.

The MTO can have a wide range of responsibilities. At one end of the spectrum, you have an operator using a standard set of instructions, designed using a cook-book approach: if such-and-such happens, perform procedure X. At the other end of the spectrum, you have a system programmer who understands the flexibility of IMS control as well as the application program and database requirements. The first approach requires good symptom-based instructions; the second requires clear guidelines and periodic auditing.

If an operator handles your operations, the two areas for which they need instructions, detailed to a level appropriate for their knowledge and responsibilities, are:

• Normal operations

  You need to document instructions for making specific resources available for committed end-user service. The instructions must be especially clear about when and how to shut down and restart IMS. If alternative network connections are part of the system design, the instructions should have a set of additional procedures for them.

  Operators who understand the end-user priorities should be allowed to change the scheduling algorithm by making reassignment of message priorities or even of message region classes.

• Error and recovery operations (triggered by symptoms or user feedback)

  These events range from temporary transaction processing problems to problems that have serious database implications. Your recovery procedures should include carefully documented and tested actions for your operators to take.

  Recommendation: Design your procedures so the operator initiates recovery actions in cooperation with your user-liaison group and your system-support personnel. Structure your operations to take advantage of as much consultation as possible. Insist that your operators record all recovery actions in a run log, including justification for decisions made.

  An important part of the operations strategy is the recovery procedures used to restart the online IMS subsystem after a failure of the operating system or the IMS control region.