JES2 Checkpoints
JES 2 maintains a snapshot of the queues on one or more checkpoint data sets.
This data can be used to re-initialise JES2 queues during a "warm" or "quick" start. This will retain all of the jobs on the spool, unless the operator manually decides that the system needs a cold start.
The checkpoints are being taken periodically while printing the SYSOUT data sets.
After a system failure, during a warm start the processing can simply resume from the checkpoint.