Summary -

In this topic, we described about the below sections -

UNIT parameter used to ask the system to place the dataset on a specific device or a group of devices or the same device as another dataset. UNIT is optional parameter.

UNIT do not required to specify with SMS. 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.

Syntax -

{UNIT=([ddd          ] [,unit-count] [,DEFER]) }
       [/ddd         ] [,P         ] [,     ]
       [/dddd        ] [,          ]
       [device-type  ]
       [group-name   ]

device-number Specifies device by a 3-digit or 4-digit hexadecimal number.
Precede a 4-digit number with a slash (/).
A 3-digit number can be specified with or without a slash.
device-type Specifies a device by its generic name which is an IBM-supplied name.
If specify the device-type sub parameter, SMS ignores it.
group-name Specifies a group of devices by a symbolic name.
The group-name is 1 through 8 alphanumeric characters.
unit-count Specifies the number of devices.
"Unit-count" is a decimal number from 1 through 59.
P Specifies the system to allocate the same number of devices from the VOLUME volume-count or SER subparameter, whichever is higher.
DEFER Specifies the system to assign the dataset to device(s)

Defaults and overrides:

If SYSOUT and UNIT coded on the same statement, the SYSOUT parameter overrides the UNIT parameter.

Example 1:


DD statement DD01 requests one 3440 tape device.

Example 2:

//  VOLUME=SER=13230,UNIT=3440

This DD statement defines a new data set and requests that the system assign any 3440 Magnetic Tape Unit.

Example 3:


This DD statement defines a cataloged data set and requests that the system assign two devices to the data set.