Application requirements for restartability

Under the QUICKSTART for MVS product, to ensure restartability, the application program must:

  • Issue checkpoints through the QUICKSTART facilities;
  • Access any necessary repositionable sequential files through the QUICKSTART facilities;
  • Identify a portion of the Working Storage Section to be designated as the Checkpoint Area. This identification can be done implicitly using Transparent Mode (where allowed) or explicitly using API Mode.

In addition, the application program should be structured according to the guidelines of the Logical Unit of Work (LUW). This approach requires that the application program be designed as a looping program, with a single transaction being processed for each iteration of the loop. The application program retrieves from the appropriate data source the next transaction to be processed at the “top” of the loop, processes the transaction in the “body” of the loop, and issues a checkpoint at the “bottom” of the loop. Most batch programs fall naturally into this structure. However, there are many variations to the LUW structure. This section discusses the most common forms of LUW, as well as other requirements for restartability.

This section contains the following topics:

 

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