This chapter describes the PL/I Checkpoint/Restart feature which provides a convenient method of taking checkpoints during the execution of a long-running program in a batch environment.
At points specified in the program, information about the current status of the program is written as a record on a data set. If the program terminates due to a system failure, you can use this information to restart the program close to the point where the failure occurred, avoiding the need to rerun the program completely.
This restart can be either automatic or deferred. An automatic restart is one that takes place immediately (provided the operator authorizes it when requested by a system message). A deferred restart is one that is performed later as a new job.
You can request an automatic restart from within your program without a system failure having occurred.
PL/I Checkpoint/Restart uses the Advanced Checkpoint/Restart Facility of the operating system. This facility is described in the books listed in Bibliography.
To use checkpoint/restart you must do the following: