Specifying whether to suspend system activity for device allocations

Sometimes DFSMShsm requests a device allocation and that request cannot be met because all tape devices are temporarily unavailable. When no tape devices are immediately available, dynamic allocation can wait for a tape device to become available before it returns to DFSMShsm or it can retry the request at a later time. If dynamic allocation waits for a device, all DFSMShsm processing soon stops until a device is allocated. If dynamic allocation does not wait and DFSMShsm retries the request later, other DFSMShsm functions can continue processing.

The WAIT and NOWAIT options of the tape device-allocation parameters (INPUTTAPEALLOCATION, OUTPUTTAPEALLOCATION, and RECYCLETAPEALLOCATION) control whether all DFSMShsm processing is suspended for a device allocation or not. The options you should use depend on:

Whether you are managing tapes in a JES2 or a JES3 environment
The number of tape devices that are available for DFSMShsm processing
How much help you provide in making tape devices available
You can make tape devices available by restricting the use of tape devices. For more information about restricting output to devices with similar characteristics, see Restricting tape device selection.

Note: The WAIT|NOWAIT option does not apply to the aggregate-backup-and-recovery support (ABARS) secondary address space. For information about specifying a wait option for ABARS, see Enabling ABARS ABACKUP and ARECOVER to wait for a tape unit allocation.