z/OS MVS JCL Reference
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UNIT parameter

z/OS MVS JCL Reference

Parameter Type: Keyword, optional

Note: With SMS, you do not need to use the UNIT parameter to specify a device for an SMS-managed data set. Use the STORCLAS parameter (described in ) or let an installation-written automatic class selection (ACS) routine select a storage class for the data set.

Also with SMS, for a non-SMS-managed data set, if your storage administrator has set a system default unit under SMS, you do not need to specify UNIT. Check with your storage administrator.

Purpose: Use the UNIT parameter to ask the system to place the data set on:
  • A specific device.
  • A certain type or group of devices.
  • The same device as another data set.

The UNIT parameter can also tell the system how many devices to assign and request that the system defer mounting the volume until the data set is opened.

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