Checkpoint/restart is a method of recording information about a job at programmer-designated checkpoints so that the job can be restarted at one of these checkpoints or at the beginning of a job step.

A checkpoint is taken when your program or the system end-of-volume function issues the CHKPT macro instruction. This macro causes the contents of the program's virtual storage area and certain system control information to be written as a series of records in a data set. The restart function retrieves records from the data set if the job terminates abnormally or produces erroneous output, and the job can be restarted. Restart can take place immediately (allowed by the operator at the console) or be deferred until the job is resubmitted. In either case, you can avoid the time-consuming process of rerunning the entire job from the beginning.