Subparameter definition

device-number

Identifies a specific 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.

Attention: Specify a device number only when necessary. When you specify a device number, the system can assign only that specific device. If the device is already being used, the job must be delayed or canceled. If the device number is changed or logically moved, the allocation request will fail.

However, for a permanently mounted direct access device, such as a 3390 Direct Access Storage, specifying a device type (UNIT=3390) and a volume serial number in the VOLUME=SER parameter has the same result as specifying a device number in the UNIT parameter.

In a JES3 system, if any DD UNIT parameter in a job specifies a device-number for a device that is JES3-managed or jointly JES3/MVS managed, Start of change either the JOB statement must contain a SYSTEM or SYSAFF parameter, End of change or the JES3 //*MAIN statement must contain a SYSTEM parameter.

For an SMS-managed tape library request where SMSHONOR is not specified, or an SMS-managed DASD request, the device number is ignored. For an SMS-managed tape library request where SMSHONOR is specified, the system attempts to allocate the specified device, provided it is in the storage group(s) assigned to the request by SMS.

device-type

Requests a device by its generic name, which is an IBM-supplied name that identifies a device by its machine type and model. For example, UNIT=3390.

When a device-type name contains a hyphen, do not enclose it in apostrophes, for example, UNIT=3400-5.

Obtain the list of device types you can specify from your installation.

If you specify the device-type subparameter, SMS ignores it.

For a 3480 Magnetic Tape Subsystem in compatibility mode, code UNIT=3400-9 or a group-name.

group-name

Requests a group of devices by a symbolic name. The installation must have assigned the name to the device(s) during system initialization or IBM must have assigned the name. The group-name is 1 through 8 alphanumeric characters.

For an SMS-managed tape library request where SMSHONOR is not specified, or an SMS-managed DASD request, the group-name is ignored. For an SMS-managed tape library request, if SMSHONOR is specified along with the group-name, the system attempts to allocate to the subset of devices in the group-name, provided that they are also selected by SMS.

Group names: A group-name can identify a single device or a group of devices. A group can consist of devices of the same or different types. For example, a group can contain two or more different types of direct access storage devices (DASD) or two or more different types of tape devices, or even a mixture of both direct access and tape devices. Note, however, that IBM does not recommend that a group contain both direct access storage devices (DASD) and tape devices.

Note: A group name is called an esoteric name in Hardware Configuration Definition (HCD) terminology.

Allocation from groups: The system assigns a device from the group. If a group consists of only one device, the system assigns that device. If the group consists of more than one device type, the units requested are allocated from the same device type. For example, if GPDA contains 3380 Disk Storage and 3390 Direct Access Storage devices, a request for two units would be allocated to two 3380s or to two 3390s.

Extending data set: If a data set that was created using the group-name subparameter is to be extended, the system allocates additional devices of the same type as the original devices. However, the additional devices may not necessarily be from the same group.

SYSALLDA: IBM assigned group-names include SYSALLDA, which contains all direct access devices defined to the system.

SYS3480R and SYS348XR: SYS3480R and SYS348XR are IBM-assigned group names. SYS3480R contains 3480, 3480X, and 3490 Magnetic Tape Subsystems. SYS348XR contains 3480X and 3490 Magnetic Tape Subsystems.

Use these group names to override the device type eligibility retrieved by the system when referencing existing 3480- or 3480 XF-formatted data sets. Specifically, use SYS3480R when you want to read 3480-formatted data sets and use SYS348XR when you want to read 3480 XF-formatted data sets.

Note: LABEL=(n,,,IN) is the system-managed tape library equivalent of either UNIT=SYS3480R or UNIT=SYS348XR.

unit-count

Specifies the number of devices for the data set. "Unit-count" is a decimal number from 1 through 59.

Number of devices allocated: The system uses the unit-count to determine how many devices to allocate. For tapes, the system uses the unit-count subparameter to allocate the specified number of system-managed or non-system-managed units. If you also specify P (for parallel mount) in the UNIT parameter, and for SMS-managed DASD, the system uses the highest of the following numbers to determine how many devices and volumes to allocate:

unit-count specified in the UNIT parameter
volume-count specified in the VOLUME parameter
number of volume serial numbers implicitly or explicitly specified

You may receive more devices than the unit-count requests if you specify VOLUME=REF or a permanently resident or reserved volume. And, if two DD statements in a step request the same volume and either DD statement requests any other volume(s), the system assigns an additional device.

Unit count for received or VOLUME=REF data sets: The system assigns one device when the DD statement receives a passed data set or refers in a VOLUME=REF subparameter to a cataloged data set or earlier DD statement for volume and unit information. Code a unit-count subparameter if the data set needs more than one device.

Unit count when device number specified: When the first subparameter requests a specific device, the unit count must be 1 or omitted. Only when the device is a communication device can the unit count be higher than 1.

Unit count when SMSHONOR specified: When SMSHONOR is specified, only the subset of devices that are selected by SMS and are within the specified group-name are eligible. When a unit count is specified, the requested number of devices are selected from the subset of devices. If the subset does not contain enough devices to satisfy the requested unit count, the request fails.

P

Asks the system to allocate the same number of devices as requested in the VOLUME volume-count or SER subparameter, whichever is higher. Thus, all volumes for the data set are mounted in parallel.

If you specify the P subparameter for system-managed DASD, the system ignores it. If you specify the P subparameter for system-managed tape libraries, the system honors it.

DEFER

Asks the system to assign the data set to device(s) but requests that the volume(s) not be mounted until the data set is opened. To defer mounting, DEFER must be specified or implied for all DD statements that reference the volume.

If you specify the DEFER subparameter for system-managed DASD, the system ignores it. If you specify the DEFER subparameter for system-managed tape libraries, the system honors it.

DEFER when data set is never opened: If you request deferred mounting of a volume and the data set on that volume is never opened by the processing program, the volume is never mounted during the job step.

Restrictions on DEFER: Do not code DEFER:

For a new data set on direct access. The system ignores DEFER.
On a SYSCKEOV DD statement.

SMSHONOR

Asks the system to honor the device number or group-name and allocate to the device number or group-name specified in the case of an SMS tape library request.

Use only device number or group-name (user-defined esoteric) when you use SMSHONOR. The following subset of devices must be consistent with libraries assigned to the storage class specified on the request or selected by ACS routines of the installation :

subset of devices that are in the specified group name.
subset of devices that are with the specified device number, which are selected by the storage class assigned to the request.

Note: If the device number or group-name does not intersect with the storage class, the request fails.

If you specify the SMSHONOR subparameter on a non-SMS system, the system ignores the keyword.

If you specify a group name in a JES3 environment, all devices in the group must be of the same device type and from the same tape library. There are no such restrictions in a non-JES3 environment.

AFF=ddname

Requests that the system allocate different data sets residing on different, removable volumes to the same device during execution of the step. This request is called unit affinity, where "ddname" is the ddname of an earlier DD statement in the same step. Use unit affinity to reduce the number of devices used in a job step; request that an existing data set be assigned to the same device(s) as another existing data set.

If you specify the UNIT=AFF subparameter for system-managed DASD, the system ignores it. If you specify the UNIT=AFF subparameter for system-managed tape libraries, the system attempts to honor it.

Under certain conditions the system ignores unit affinity. See z/OS MVS JCL User's Guide for more information.

In a JES3 environment, UNIT=AFF=ddname may not be honored. See z/OS MVS JCL User's Guide and z/OS HCD Planning for information about device eligibility and unit affinity.

Restrictions on UNIT=AFF: Do not code UNIT=AFF=ddname:

With DISP=NEW if the data set referenced in the AFF subparameter resides on a direct access device. This restriction applies only to non-SMS-managed DASD. If coded, the system terminates the job. If the referenced data set can be allocated to either tape or DASD, the system allocates both requests to tape devices.
On a DD * or DD DATA statement or on a DD statement containing a SUBSYS parameter. The system ignores the UNIT=AFF and defaults the device to SYSALLDA.
When the DD statement referenced in the AFF subparameter contains FREE=CLOSE.
With the STORCLAS parameter.
With an affinity specification to an earlier DD statement that requests SYS3480R or SYS348XR on the group-name subparameter, unless volume affinity also exists. Volume affinity exists when two DD statements both reference a data set on the same volume. Do not also specify DISP=OLD or DISP=MOD; attempting to write 3480 data to a 3490 drive, or 3490 data to a 3480 drive, will fail during OPEN processing with ABEND 813-04 accompanied by message IEC149I.