Subparameter definition

• The system is not to allocate an output data set to the volume unless the volume is specifically requested, such as in a VOLUME=SER subparameter.
• If tape, the volume is to be demounted after the data set is closed, unless RETAIN is also coded or the DD DISP parameter specifies PASS.
• If a demountable direct access volume, the volume is to be demounted after the data set is closed.

RETAIN has no effect on the handling of direct access volumes.

For JES3-managed tape devices, JES3 does not accept the RETAIN parameter after reaching the end of the job. However, if RETAIN is coded and the tape volume is to be shared with a later step, JES3 designates the volume as retained. JES3 also ignores the RETAIN parameter when issuing its KEEP/RETAIN messages.

If the volume sequence number is not specified, the system processes the first volume.

For new data sets, the system ignores the volume sequence number.

DASD volumes cannot be removed from the drive. Therefore, the number of volumes for a data set is the same as the number of drives for the data set. This number cannot exceed 59.

For a tape data set, the number of volumes can be more or less than the number of drives. The number of drives cannot exceed 59. The number of volumes cannot exceed 255. The system uses the unit count to determine how many tape devices to allocate. However, if you also specify P (for parallel mount) in the UNIT parameter, the system might use the value that is specified for the volume count to determine how many devices and volumes to allocate. See the unit-count description in Subparameter definition.

Volume count and serial numbers: When the volume count is greater than:

• The number of volume serials that are coded in the SER sub parameter, OR
• The number of volume serials that the system retrieved from the catalog, OR
• The number of volume serials that the system retrieved from VOL=REF OR
• The number of volume serials that the system retrieved from a passed data set,

then, the system can assign more volumes. If the volume count is smaller than the number of volume serials that are coded or retrieved, the system will assign a volume count based on the number of coded or retrieved volume serials.

If a data set might need more volumes than the number of volume serials that are coded, specify a volume count equal to the total number of volumes that might be used. Requesting more volumes in the volume count ensures that the data set can be written on more volumes if it exceeds the requested volumes.

Volume count for nonspecific requests: If the request is for a nonspecific, public volume on a direct access device, the system ignores the volume count and allocates the number of volumes in the UNIT count subparameter. If the request is for a nonspecific, private volume, then the system acts as if a volume count greater than one was coded, and allocates the number of volumes that are given in the volume count.

Volume count for system-managed DASD data sets: You cannot specify a volume count for an existing system-managed DASD data set. (If you do, the system ignores it.) When you create a new system-managed DASD data set, the volume count defined in the data class might be overridden by using the volume-count subparameter. However, if the volume-count subparameter specifies a value greater than 59, the system sets the volume count to a maximum of 59. The maximum volume count for a VSAM or System-Managed DASD data set is 59.

Volume count for tape data sets: The volume count is the upper limit for the number of volumes on which the data set can reside. The maximum value is 255. When creating a new data set, if you do not specify a volume count on the volume-count subparameter on the DD statement and the data set has a data class, the system will use the volume count in that data class. If the data class does not have a volume count defined, then the system allows a maximum of 255 volumes.

When your job extends the data set to another volume, the system extracts the volume count from the data class as the data class is defined. If your data set does not have a data class or the data class has no volume count, then the system uses a maximum count of 255.

When extending an existing data set, if you do not specify a volume count on the volume-count subparameter of the DD statement, then the system allows a maximum of 255 volumes.

The system allows a data set to reside on more volumes than specified on the volume-count subparameter or the data class volume count, but never more than 255 volumes. If the volume count is 1 through 5, then the maximum number of volumes is 5. If the volume count is greater than 5, then the maximum number of volumes is 5 plus a multiple of 15 volumes. For example, if the volume count is 6 through 20, then the maximum number of volumes is 20. If the volume count is 21 through 35, then the maximum number of volumes is 35.

Volume count for system-managed tape data sets: If you specify a volume count and DISP=PASS on a DD statement, the system passes the volume count to subsequent receiving steps within the job. This might cause the system to allocate more devices than expected to the receiving DD. Coding UNIT=AFF in the receiving step's DD results in the optimum number of devices being allocated to the receiving DD. For more information about the number of devices allocated, see z/OS MVS JCL User's Guide.

You can code a maximum of 255 volume serial numbers on a DD statement. The maximum number of volume serial numbers for a VSAM or SMS-managed data set is 59.

Do not specify duplicate volume serial numbers in a SER subparameter. Each volume must have a unique volume serial number, regardless of whether it is a tape or disk volume.

Do not code a volume serial number as SCRTCH, PRIVAT, or Lnnnnn (L with five numbers); these are used in messages to ask the operator to mount a volume. SCRTCH is used when the data set being created on the non-specific volume is temporary [DISP=(NEW,DELETE) or DSN=&&tempname]. PRIVAT is used for all other cases of non-specific volumes. Lnnnnn is used by the system to represent the volume serial number of an NL (unlabeled) tape. Do not code a volume serial number as MIGRAT, which is used by the Hierarchical Storage Manager DFSMShsm for migrated data sets.

See the SPACE parameter for more information about space allocation.

Some printers might not be able to print certain special characters. Consider this when using special characters as part of a volume serial number.

For a permanently mounted direct access device, such as a 3390 Direct Access Storage, specifying a volume serial number and UNIT=3390 has the same result as specifying a device number in the UNIT parameter.

For new SMS-managed DASD data sets:

DASD

For SMS-managed library tape volumes: For SMS-managed Library Tape volume, the Guaranteed Space storage class attribute is ignored and the system allocates to the specified volume.

dsname

Names a cataloged or passed data set. The system assigns this data set to the same volumes containing the cataloged or passed data set.

When dsname names a passed data set, the reference must appear on a DD statement before the receiving DD statement. (After a passed data set is received, the passed data set information is no longer available.)

When the dsname contains special characters other than the periods used in a qualified name, enclose it in apostrophes.

The dsname can be an alias name or a catalog name. The dsname cannot be a generation data group (GDG) base name or a member name of a non-GDG data set.

If the referenced cataloged data set is migrated, it is recalled before assigning the volumes to the data set.

*.ddname

Asks the system obtain the volume serial numbers from an earlier DD statement with the name ddname in the same job step.

*.stepname.ddname

Asks the system to obtain the volume serial numbers from a DD statement with the name ddname, in an earlier step with the name stepname, in the same job.

*.stepname.procstepname.ddname

Asks the system to obtain the volume serial numbers from a DD statement in a cataloged or in-stream procedure. Stepname is the name of the job step that calls the procedure, procstepname is the name of the procedure step that contains the DD statement, and ddname is the name of the DD statement.

Referenced data set not opened: When REF refers to a DD statement in a previous step and the data set was not opened, the system allocates a device that has the widest range of eligibility to meet both DD statement requests. Thus, the system might allocate a device for which the referring data set is not eligible. To prevent this problem for tape data sets, always code the DCB DEN subparameter, or the DCB TRTCH subparameter on a DD statement that you plan to reference.

References to multivolume tape data sets: When REF refers to a data set residing on more than one tape volume, the system allocates all volumes to the referencing DD when it represents an OLD data set, that is, a data set that existed before the current job step. For a NEW tape data set the system allocates only the last volume of a referenced multivolume tape data set.

If an earlier job step extends the referenced data set to more volumes, or adds or extends an earlier data set so that the referenced data set resides on a later volume, the new volume information is available to the referencing DD statement.

If the referenced data set already exists and has volume serial numbers that are explicitly specified, then the last listed volume serial is used even if the earlier data set exists on or is written to fewer volumes.

If the referenced data set is new and has specific volume serials, then the last listed volume serial is used even if the data set is written with fewer volumes.

In either of these cases, the allocation of the referencing data set is likely to fail.

References to multivolume direct access data sets: When REF refers to a data set that resides on more than one direct access volume, the system allocates all of the volumes.

If a DD statement that is requesting a new data set has a unit count and volume count greater than one but specifies no volume serial numbers, one volume is allocated. If a second DD statement within the same step requests the same data set, the same volume is allocated to it. If this job step extends the data set to more volumes, this new volume information is not available to the second DD statement.

Two or more DD statements in the same step can request the same data set. However, if the data set is extended to additional volumes in that step, the additional volume information is not available to the second or succeeding DD statements within the step.

References to DD statements with UNIT group names: When REF refers to a DD statement containing a UNIT group-name subparameter, the system allocates a device of the same type that is actually used for the referenced data set, but not necessarily a device in the referenced group-name.

References to VSAM data sets: When REF refers to a multivolume VSAM data set, the system allocates a device of the same type as the first device type that is used for the referenced VSAM data set.

If the ACS routine attempts to make the referencing data set SMS-managed, SMS fails the allocation with message IGD305I.

Do not refer to in-stream data sets: Do not refer to a DD *, DD DATA, or DD SYSOUT statement. The system ignores the reference and defaults the device name to SYSALLDA, which is the group name for all direct access devices that are defined to the system.

References to DUMMY data sets: If ddname refers to a DD DUMMY statement, the data set for this DD statement is also assigned a dummy status.