Spool data sets and checkpoint
Spooling refers to process of communicating data to another program by placing it in a temporary working area, where the other program can access it at some later point in time. Spooling is often used when devices access data at different rates. The temporary working area provides a waiting station where data can reside while a slower device can process it at its own rate.
In a JES3 system, spool serves:
As a buffer between input devices and routines that read input data, and between routines that write output ...

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