This DD statement is required in order to restart a MAXSORT which is task-invoked or includes a user exit routine because in these cases MAXSORT cannot be restarted from a breakpoint. The standard OS/VS Checkpoint-Restart feature is used. Both automatic Checkpoint-Restart and deferred Checkpoint-Restart capabilities are supported (see Performance Considerations). Checkpoints are taken at the end of each intermediate sort or merge.
The SORTBKPT DD statement must be specified in addition to the SORTCKPT DD statement even when MAXSORT cannot be restarted from a breakpoint.
A MAXSORT with an E35 exit does not require the SORTCKPT DD statement.