• 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 honor 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 will process the first volume.

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

Volume count for tape data sets:

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

If you do not code a volume count and volume serial number, the system can extend an existing cataloged data set that resides on a removable volume up to 20 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, the system treats it like a specific request if the volume count is more than one and allocates the number of volumes 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 will ignore it.) When you create a new system-managed DASD data set, the volume count defined in the data class may be overridden by using the volume-count subparameter. However, if the volume-count subparameter specifies a value greater then 59, the system will set 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 system-managed tape data sets: If you specify a volume count and DISP=PASS on a DD statement, the system will pass the volume count to subsequent receiving steps within the job. This may cause the system to allocate more devices than expected to the receiving DD. Coding UNIT=AFF in the receiving step's DD will result in the optimum number of devices being allocated to the receiving DD. For more information about the number of devices allocated, refer to the z/OS MVS JCL User's Guide. When you create a new system-managed TAPE data set, the volume count defined in the data class may be overridden by using the volume-count subparameter. If you do not provide a volume count parameter than the volume count specified in the data class would be used.

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 dataset 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 as the "volser" 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. When using some typewriter heads or printer chains, a volume serial number may be unrecognizable if you code certain special characters.

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

// ddname2 DD DSN=TSOUSR2.TAPE.GDGNAME(0),DISP=SHR,VOL=REF=*.
stepname.ddname1

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.

The dsname can be a GDG relative generation member, but since it contains special characters (the parentheses) it must be enclosed in apostrophes. It is important to be aware that while a GDG relative generation name in the DSNAME parameter always resolves to the state of the GDG index as of the beginning of the job, a GDG relative generation name in the dsname sub-parameter of the VOLUME parameter always resolves to the state of the GDG index as of the beginning of the step. For example if, at the beginning of a job, the latest generation of a dataset was G0007V00, and steps 1 and 2 of the job each created a new generation, then the following JCL for step 3 of the job would be resolved as shown:

//STEP3  EXEC PGM=pgmname
//DD1    DD   DSN=gdgname(0),
//            DISP=SHR,
//            VOL=REF='gdgname(0)'

DSN=gdgname(0) would resolve to generation G0007V00, since that was the zeroeth generation at the beginning of the job.

VOL=REF=gdgname(0) would resolve to generation G0009V00, since that was the zeroeth generation at the beginning of the step.

By the same token,

//STEP3  EXEC PGM=pgmname
//DD1    DD   DSN=gdgname(+3),
//            DISP=NEW,
//            VOL=REF='gdgname(+2)'

DSN=gdgname(+3) would resolve to generation G0010V00, since that would be the +3 generation at the beginning of the job.

VOL=REF=gdgname(+2) would resolve to generation G0011V00, since that would be the +2 generation at the beginning of the step. Since G0011V00 would not yet exist, it would not be possible to refer to it as an existing dataset, and so this JCL would fail.

*.ddname

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

*.stepname.ddname

Asks the system to obtain the volume serial numbers from DD statement, ddname, in an earlier step, 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 prior to 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 explicitly specified, then the last listed volume serial is used even if the earlier data set actually 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 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 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 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.

Label type picked up from referenced statement: When REF is coded, the system also copies the LABEL label type subparameter from the referenced DD statement.