Optional Parameters

ACCODE(access code)

Assigns the accessibility code for an ISO/ANSI output tape data set, which protects it from unauthorized use. You can use up to eight characters in the access code, but ISO/ANSI validates only the first character. The ACCODE can now be any of the following 57 ISO/ANSI a-type characters: blank, upper case letters A-Z, numeric 0-9, or one of the special characters !*"%&'()+,-./:;<=>?_ Password protection is supported for ANSI tape data sets under the PASSWORD/NOPWREAD options on the LABEL parameter. Password access overrides any ACCODE value if you use both options.

ALTFILE(name)

The name of the SYSIN subsystem data set that is to be allocated, and can be up to eight characters. The system uses this parameter primarily in the background.

This gives the length in bytes of the average block.

AVGREC(U|K|M)

Determines the size of the average record block. You can use the following values:

U: Use the primary and secondary quantities as given on the SPACE parameter.
K: Multiply primary space quantity and secondary space quantity by 1024 (1 KB).
M: Multiply primary space quantity and secondary space quantity by 1,048,576 (1 MB).

Use the AVGREC parameter to define a new data set when:

The units of allocation that is requested for storage space are records.
The primary and secondary space quantities used with the SPACE parameter represent units, thousands, or millions of records.

When you use AVGREC with the SPACE parameter, the first subparameter for the SPACE parameter must give the average record length of the records.

Use the AVGREC parameter when you want to show records as the units of allocation. You can also use the AVGREC parameter to override the space allocation defined in the data class for the data set.

If SMS is not active, the system checks the syntax and then ignores the AVGREC parameter.

BFALN(F|D)

Gives is the boundary alignment of each buffer:

F: Each buffer starts on a fullword boundary that might not be a doubleword boundary.
D: Each buffer starts on a doubleword boundary.

If you do not use this parameter, the system defaults to a doubleword boundary.

BFTEK(S|E|A|R)

Is the type of buffering that you want the system to use, such as:

S: Simple buffering
E: Exchange buffering
A: Automatic record area buffering
R: Record buffering

BFTEK(R) is not compatible with partitioned data sets extended (PDSE) and results in an error if used with the DSNTYPE(LIBRARY) parameter.

BLKSIZE(value)

The data control block (DCB) block size for the data set. If the data set is not on tape and is not dummy, the maximum allowable value for the block size is 32760. If the data set is on tape or dummy and the program uses LBI, the maximum allowable value for the block size is 256K. If you code the K, it multiplies the value by 1024. "LBI" stands for large block interface and means that the application program coded the BLKSIZE parameter on a DCBE macro. You can specify BLKSIZE for NEW or MOD data sets.

For direct access storage device (DASD) data sets: If you do not use BLKSIZE, the system determines an optimal DCB block size for the new data set. To create the DCB block size:

The system determines the block size if the record format is not U (undefined) and you do not assign the block size.
You can assign the block size through the BLKSIZE parameter.
You can use the LIKE parameter to obtain the block size from an existing model data set.
If you do not assign BLKSIZE or LIKE, the system can determine the block size from the BLOCK parameter.

The block size that you assign for the DCB must be consistent with the requirements of the RECFM parameter. If you use:

RECFM(F), the block size must be equal to, or greater than, the logical record length.
RECFM(FB), the block size must be an integral multiple of the logical record length.
RECFM(V), the block size must be equal to, or greater than, the largest block in the data set. (For unblocked variable-length records, the size of the largest block must allow space for the 4-byte block descriptor word, in addition to the largest logical record length. The logical record length must allow space for a 4-byte record descriptor word.)
RECFM(VB), the block size must be equal to, or greater than, the largest block in the data set. For block variable-length records, the size of the largest block must allow space for the 4-byte block descriptor word, in addition to the sum of the logical record lengths that will go into the block. Each logical record length must allow space for a 4-byte record descriptor word.
Because the number of logical records can vary, estimate the optimum block size and the average number of records for each block, based on your knowledge of the application that requires the I/O.
RECFM(U) and BLKSIZE(80), one character is truncated from the line if the data set is the TSO terminal. That character (the last byte) is reserved for an attribute character.

For PDSEs:

The system chooses the BLKSIZE if you do not explicitly specify it. If BLKSIZE is given, the system treats the BLKSIZE as the length of the simulated block. For create mode processing, the logical record length is equal to the block size if LRECL is not given. If you use LRECL, BLKSIZE must conform to the LRECL and RECFM definitions. If you use:
RECFM(F)

BLKSIZE must equal LRECL

RECFM(FB) or RECFM(FBS)

BLKSIZE must be a multiple of LRECL

RECFM(V) or RECFM(VB)

BLKSIZE must be at least four bytes larger than LRECL

RECFM(VBS)

BLKSIZE must be at least eight bytes.
For input or update processing, the block size must conform to the currently defined record length. The BLKSIZE given when the data set was created is the default. However, you can use any BLKSIZE if it conforms to the record length definition.

BUFL(buffer-length)

The length, in bytes, of each buffer in the buffer pool. Substitute a decimal number for buffer-length. The number must not exceed 32,760. If you omit this parameter and the system acquires buffers automatically, the BLKSIZE and KEYLEN parameters supply the information needed to establish buffer length.

BUFNO(number-of-buffers)

The number of buffers that are assigned for data control blocks. Substitute a decimal number for number-of-buffers. The number must never exceed 255. You might be limited to a smaller number of buffers depending on the available amount of virtual storage in your address space. The following shows how to get a buffer pool and the action required:

Method: Action
BUILD macro instruction: You must use BUFNO
GETPOOL macro instruction: The system uses the number that you assign for GETPOOL
Automatically with BPAM or BSAM: You can use BUFNO if the application program was designed to exploit it with the GETBUF macro.
Automatically with QSAM: You can omit BUFNO and accept two buffers

BUFOFF({block-prefix-length|L})

Defines the buffer offset. The block-prefix-length must not exceed 99. L specifies the block prefix field is 4 bytes long and contains the block length.

DATACLAS(data-class-name)

This is the 1-to-8 character name of the data class for either SMS or non-SMS-managed data sets. If you do not assign DATACLAS for a new data set and the storage administrator has provided an automatic class selection (ACS) routine, the ACS routine can select a data class for the data set. If you assign DATACLAS for an existing data set, SMS ignores it. If SMS is not active, the system checks the syntax and then ignores the DATACLAS parameter.

If you use the data class, you do not need to list all the attributes for a data set. For example, the storage administrator can provide RECFM, LRECL, RECORG, KEYLEN, and KEYOFF as part of the data class definition. However, you can override the DATACLAS parameter by explicitly defining the appropriate parameters in the ALLOCATE command.

The data class defines these data set allocation attributes:

Data set organization:
- Record organization (RECORG)
- Record format (RECFM)
Record length (LRECL)
Key length (KEYLEN)
Key offset (KEYOFF)
Space allocation
- AVGREC
- SPACE
Expiration date (EXPDT) or retention period (RETPD)
Volume count (VOLUME)
For VSAM data sets, the following:
- Control interval size (CISIZE)
- Percent free space (FREESPACE)
- Sharing options (SHAREOPTIONS)

SHAREOPTIONS is assumed to be (3,3) when you use RLS.

Table 1. Data Class Attributes vs. Data Set Organization
Attributes	KS	ES	RR	LDS
CISIZE	X	X	X	X
FREESPACE	X
KEYLEN	X
KEYOFF	X
LRECL	X	X	X
SHAREOPTIONS	X	X	X	X
SPACE	X	X	X	X
Volume Count	X	X	X	X

DEN(0|1|2|3|4)

Gives the magnetic tape density as follows:

0: 200 bpi/7 track
1: 556 bpi/7 track
2: 800 bpi/7 and 9 track
3: 1600 bpi/9 track
4: 6250 bpi/9 track (IBM® 3420 Models 4, 6, and 8)

DIAGNS(TRACE)

The Open/Close/EOV trace option that gives a module-by-module trace of the Open/Close/EOV work area and your DCB.

DIR(integer)

Gives the number of 256 byte records for the directory of a new partitioned data set. You must use this parameter to allocate a new partitioned data set.

specifies the type of data set to be allocated

LIBRARY: specifies a partitioned data set extended (PDSE).
PDS: specifies a partitioned data set (PDS).
HFS: specifies a UNIX file system. IBM® recommends not using this type of data set. IBM recommends defining a VSAM linear data set and defining a z/OS® file system (zFS) in it.
PIPE: specifies a first-in first-out (FIFO) special file, which is also called a named pipe. If you specify PIPE, you must also specify PATH and not DATASET or DSNAME.
LARGE: specifies a large format sequential data set. It can have a size greater than 65535 tracks on a single volume.
BASIC: specifies a basic format sequential data set. It is limited to no more than 65535 tracks per volume, which is about 3.6 GB.
EXTREQ: specifies that the data set must be extended format. It can be sequential or VSAM. It can be striped, compressed format or neither.
EXTPREF: specifies that the data set should be allocated as extended format, if possible. If not possible, allocate the data set as basic format.

If you omit DSNTYPE, the type of data set is determined by other data set attributes, the data class for the data set, or an installation default.

For more information on PDSE, see z/OS DFSMS Using Data Sets.

DSORG(DA|DAU|PO|POU|PS|PSU)

The data set organization as:

DA: Direct access
DAU: Direct access unmovable
PO: Partitioned organization
POU: Partitioned organization unmovable
PS: Physical sequential
PSU: Physical sequential unmovable

When you allocate a new data set and do not use the DSORG parameter, these occur:

If you assign a non-zero to the DIR parameter, DSORG defaults to the partitioned organization (PO) option.
If you do not assign a value to the DIR parameter, DSORG defaults to the physical sequential (PS) option.
The system does not store default DSORG information into the data set until a program opens and writes to the data set.

With PDSEs, the PSU and POU options are incompatible and result in an error if used with DSNTYPE(LIBRARY) while the data set is open for output. If the data set is open for input or update, PSU and POU are ignored.

To indicate the data set organization for VSAM data sets, see RECORG.

[EATTR(NO | OPT)]

A data set level attribute specifying whether a data set can have extended attributes (format 8 and 9 DSCBs) and optionally reside in EAS.

NO: No extended attributes. The data set can not have extended attributes (format 8 and 9 DSCBs) and cannot reside in EAS. This is the default behavior for non-VSAM data sets.
OPT: Extended attributes are optional. The data set can have extended attributes (format 8 and 9 DSCBs) and can optionally reside in EAS. This is the default behavior for VSAM data sets.

EROPT(ACC|SKP|ABE)

The option you want to run if an error occurs when the system reads or writes a record. They are:

ACC: Accept the block of records in which the error was found
SKP: Skip the block of records in which the error was found
ABE: End the task abnormally

EXPDT(year-day)|RETPD(no.-of-days)

Expiration date or the retention period. The MGMTCLAS maximum retention period, if given, limits the retention period in this parameter. The system ignores these parameters for temporary data sets.

EXPDT(year-day)

Specifies the data set expiration date. Specify the expiration date in the form yyyy/ddd, where yyyy is a four-digit year (to a maximum of 2155) and ddd is the three-digit day of the year from 001 through 365 (for non-leap years) or 366 (for leap years).

The following four values are "never-expire" dates: 99365, 99366, 1999365, and 1999366. Specifying a "never-expire" date means that the PURGE parameter will always be required to delete the data set. For related information, see the "EXPDT Parameter" section of z/OS MVS JCL Reference.

Note:

Any dates with two-digit years (other than 99365 or 99366) will be treated as pre-2000 dates. (See note 2.)
Specifying the current date or a prior date as the expiration date will make the data set immediately eligible for deletion.

EXPDT and RETPD are mutually exclusive.

RETPD(no.-of-days)

Data set retention period in days. It can be a one-to-five-digit decimal number.

RETPD and EXPDT are mutually exclusive.

KEEP|CATALOG

A command processor can modify the final disposition with these parameters.

KEEP: This retains the data set by the system after step termination.
CATALOG: This retains the data set in a catalog after step termination.

KEYLEN(bytes)

This is the length, in bytes, of each of the keys used to locate blocks of records in the data set when the data set resides on a direct access device.

If an existing data set has standard labels, you can omit this parameter and let the system retrieve the key length from the standard label. If a key length is not supplied by any source before you enter, the system assumes an OPEN macro instruction of zero (no keys). This parameter is mutually exclusive with TRTCH.

When you want to define the key length or override the key length defined in the data class (DATACLAS) of the data set, use KEYLEN. The number of bytes is:

1 to 255 for a record organization of key-sequenced (RECORG(KS))
0 to 255 for a data set organization of physical sequential (PS) or partitioned (PO)

For PDSEs, you can use 0 or 8. Use 8 only when opening the PDSE for input. Any other value results in an error.

KEYOFF(offset)

This shows the key position (offset) of the first byte of the key in each record. Use it to define key offset or override the key offset defined in the data class of the data set. It is only for a key-sequenced data set (RECORG=KS).

Use KEYOFF parameter to allocate both SMS-managed and non-SMS-managed data sets. If SMS is not active, however, the system checks syntax and then ignores the KEYOFF parameter.

LABEL(type)

This selects the label processing, one of: SL, SUL, AL, AUL, NSL, NL, LTM, or BLP, which correspond to the JCL label-types.

For VSAM data sets, the system always uses SL, whether you define SL or SUL or neither. NSL, NL, and BLP do not apply to VSAM data sets.

LIKE(model-dsname)

This names a model data set. The system uses these attributes as the attributes of the new data set that is being allocated. The model data set must be cataloged and must reside on a direct access device. The volume must be mounted when you enter the ALLOCATE command.

Note: TSO naming conventions apply when assigning model-dsname.

When the ALLOCATE command assigns attributes to a new data set, these attributes are copied from the model data set if SMS is active:

AVGREC: Size of average record block (kilobyte, megabyte)
BLOCK, AVBLOCK,
TRACKS, CYLINDERS: Space unit
DIR: Directory space quantity
DSORG: Non-VSAM data set organization
KEYLEN: Key length
KEYOFF: Key offset
LRECL: Logical record length
RECFM: Record format
RECORG: VSAM data set organization
SPACE: Primary and secondary space quantities.

The system copies these attributes only if SMS is not active:

BLKSIZE: Block size
EXPDT: Data set expiration date
OPTCD: Optional services code (for ISAM data sets only)
Note to Reviewers: OPTCD to be deleted
VSEQ: Volume sequence number.

You can still use the LIKE parameter even if you do not have an existing data set with the exact attributes you want to assign to a new data set. You can use ALLOCATE attributes to override any model data set attributes you do not want assigned to the new data set.

When you use this:

LIKE must be used with the NEW parameter; it cannot be used with OLD, SHR, or MOD.
Use LIKE with the DATASET parameter; it cannot be used with FILE.
Only one dsname can be given in the DATASET parameter.
The system does not copy the block size from the model data set when SMS is active. If you do not show a block size in the ALLOCATE command, the system determines an optimal block size to assign to the data set.
When SMS is active, attributes copied from the model data set override attributes from the data class.
If you allocate the new data set with a member name (indicating a partitioned data set), the system prompts you for directory blocks unless that quantity is either shown in the ALLOCATE command or defaulted from the LIKE data set.
If the new data set name is indicated with a member name, but the model data set is sequential and you have not given the quantity for directory blocks, you are prompted for directory blocks.

If you define the directory value as zero and the model data set is a PDS, the system allocates the new data set as a sequential data set.

The LIKE, REFDD, and USING operands are mutually exclusive. Refer to z/OS TSO/E Command Reference for additional information on the USING operand.

LIMCT(search-number)

This is the number of blocks or tracks that the system should search for a block or available space. The number must not exceed 32760.

LRECL({logical-record-length|(nnnnnK|X)})

This is the length, in bytes, of the largest logical record in the data set. You must define this parameter for data sets that consist of either fixed-length or variable-length records.

Use the DATACLAS parameter in place of LRECL to assign the logical record length. If SMS is active and you use LRECL, the system determines the block size.

If the data set contains undefined-length records, omit LRECL.

The logical record length must be consistent with the requirements of the RECFM parameter and must not exceed the block size (BLKSIZE parameter), except for variable–length spanned records. If you use:

RECFM(V) or RECFM(V B), then the logical record length is the sum of the length of the actual data fields plus four bytes for a record descriptor word.
RECFM(F) or RECFM(F B), then the logical record length is the length of the actual data fields.
RECFM(U), omit the LRECL parameter.

LRECL(nnnnnK) allows users of ANSI extended logical records and users of QSAM "locate mode" to assign a K multiplier to the LRECL parameter. nnnnn can be a number within 1-16384. The K indicates that the value is multiplied by 1024.

For variable-length spanned records (VS or VBS) processed by QSAM (locate mode) or BSAM, use LRECL (X) when the logical record exceeds 32,756 bytes.

For PDSEs, the meaning of LRECL depends upon the data set record format:

Fixed Format Records. For PDSEs opened for output, the logical record length (LRECL) defines the record size for the newly created members. You cannot override the data set control block (DSCB) (LRECL); an attempt to do so will result in an error.
Variable Format Records. The LRECL is the maximum record length for logical records that are contained in members of the PDSE.
Undefined Format Records. The LRECL is the maximum record length for records that are contained in members of the PDSEs.

MGMTCLAS(management-class-name)

For SMS-managed data sets: This is the 1-to-8 character name of the management class for a new data set. When possible, do not use MGMTCLAS. Allow it to default through the ACS routines.

After the system allocates the data set, attributes in the management class define:

The migration of the data set. This includes migration both from primary storage to migration storage, and from one migration level to another in a hierarchical migration scheme.
The backup of the data set. This includes frequency of backup, number of versions, and retention criteria for backup versions.

If SMS is not active, the system checks the syntax and ignores the MGMTCLAS parameter.

MAXVOL(count)

This is the maximum number (1-255) of volumes upon which a data set can reside. This number corresponds to the count field on the VOLUME parameter in JCL. Use this to override the volume count attribute defined in the data class of the data set.

If VOLUME and PRIVATE parameters are not given, and MAXVOL exceeds UCOUNT, the system removes no volumes when all the mounted volumes have been used, causing abnormal termination of your job. If PRIVATE is given, the system removes one of the volumes and mounts another volume in its place to continue processing.

MAXVOL overrides any volume count in the data class (DATACLAS) of the data set.

Your user attribute data set (UADS) must contain the MOUNT attribute. Use of this parameter implies PRIVATE.

NEW

This creates a data set. For new partitioned data sets, you must use the DIR parameter. If you assign a data set name, the system keeps and catalogs a NEW data set. If you do not assign a data set name, the system deletes the data set at step termination.

NCP(number-of-channel-programs)

This gives the maximum number of READ or WRITE macro instructions for BSAM or BPAM that are allowed before the application program issues a CHECK or WAIT macro instruction. The number must not exceed 255. If you wish to use chained scheduling, you or your program must assign an NCP value greater than 1. If you omit the NCP parameter, the default depends on the application program. If the program takes no action, the default value is 1. Your program might be limited to a value smaller than 255 depending on the available amount of virtual storage in your address space.

POSITION(sequence-no.)

This is the relative position (1-65535) of the data set on a multiple data set tape. The sequence number corresponds to the data set sequence number field of the label parameter in JCL.

PRIVATE

This assigns the private–volume use attribute to a volume that is neither reserved nor permanently in resident. It corresponds to the PRIVATE keyword of the VOLUME parameter in JCL.

If you do not use VOLUME and PRIVATE parameters and MAXVOL exceeds UCOUNT, the system removes no volumes when all the mounted volumes have been used, causing abnormal termination of your job. If you use PRIVATE, the system removes one of the volumes and mounts another volume to continue processing.

PROTECT

This RACF-protects the DASD data set or the first data set on a tape volume.

For a new permanent DASD data set, the status must be NEW or MOD, treated as NEW, and the disposition must be either KEEP, CATALOG, or UNCATALOG. With SMS, SECMODEL overrides PROTECT.
For a tape volume, the tape must have an SL, SUL, AL, AUL, or NSL label. The file sequence number and volume sequence number must be one (except for NSL). You must assign PRIVATE as the tape volume use attribute.

The PROTECT parameter is not valid if a data set name is not given, or if the FCB parameter or status other than NEW or MOD is used.

RECFM(A,B,D,F,M,S,T,U,V)

This sets the format and characteristics of the records in the data set. They must be completely described by one source only. If they are not available from any source, the default is an undefined-length record. See also the RECFM subparameter of the DCB parameter in z/OS MVS JCL Reference for a detailed discussion.

Use these with the RECFM parameter:

A: To show the record contains ASCII printer control characters
B: To indicate the records are blocked
D: For variable length ASCII records
F: For fixed length records.
M: For records with machine code control characters.
S: For fixed-length records, the system writes the records as standard blocks (there must be no truncated blocks or unfilled tracks except for the last block or track). For variable-length records, a record can span more than one block. Exchange buffering, BFTEK(E), must not be used.
T: The records can be written onto overflow tracks, if required. Exchange buffering or BFTEK(E) cannot be used.
U: The records are of undefined length.
V: Shows variable length records.

You must provide one or more values for this parameter.

For PDSEs, these statements apply:

RECFM can be partially modified from the value that is saved in the DSCB when creating members.
In a PDSE that is created as fixed or fixed blocked, members must always be created with fixed–length logical records. However, the attribute of blocked might change between member creates. The first record format assigned to the PDSE is the default for member creates. The characteristic of blocked might not change during an open.
Attempts to overwrite the record format characteristic of F, U, or V with another value from that set causes a system error.
RECFM(A) and RECFM(M) are compatible with PDSEs.

RECFM and RECORG are mutually exclusive.

RECORG(ES|KS|LS|RR)

Determines the organization of the records in a new VSAM data set. To override the record organization defined in the data class (DATACLAS) of the data set, use RECORG.

You can assign:

ES: For a VSAM entry-sequenced data set
KS: For a VSAM key-sequenced data set
LS: For a VSAM linear space data set. You cannot access linear data sets with VSAM record level sharing (RLS).
RR: For a VSAM relative record data set

If you do not use RECORG, SMS assumes a non-VSAM data set.

RECORG and RECFM are mutually exclusive. To define the data set organization for a non-VSAM data set, see DSORG.

Exception: You can use the RECORG parameter to allocate both SMS-managed and non-SMS-managed data sets. If SMS is not active, however, the system checks the syntax and ignores the RECORG parameter.

REFDD(file-name)

This is the file name of an existing data set whose attributes are copied to a new data set. The system copies these attributes to the new data set:

Data set organization:
- Record organization (RECORG)
- Record format (RECFM)
Record length (LRECL)
Key length (KEYLEN)
Key offset (KEYOFF)
Space allocation
- AVGREC
- SPACE

The system does not copy the retention period (RETPD) or expiration date (EXPDT) to the new data set.

LIKE and REFDD are mutually exclusive.

Exception: You can use the REFDD parameter to allocate both SMS-managed and non-SMS-managed data sets. If SMS is not active, however, the system checks the syntax and then ignores the REFDD parameter.

RELEASE

To delete unused space when the data set is closed.

If you use RELEASE for a new data set with the BLOCK or BLKSIZE parameter, then you must also use the SPACE parameter.

REUSE

Frees and reallocates the file name if it is currently in use.

You cannot use the REUSE parameter to reallocate a file from a disposition of OLD to a disposition of SHR. However, you can first free the file with OLD, then reallocate it with SHR.

ROUND

Allocates space equal to one or more cylinders. Use this only when you request space in units of blocks. This parameter corresponds to the ROUND parameter in the SPACE parameter in JCL.

SECMODEL(profile-name[,GENERIC])

Names an existing RACF® profile to copy to the discrete profile. Use SECMODEL when you want a different RACF data set profile from the default profile selected by RACF, or when there is no default profile. The model profile can be a:

RACF model profile
RACF discrete data set profile
RACF generic data set profile

Use GENERIC to state the profile name as a generic data set profile.

The system copies this information from the RACF data set profile to the discrete data set profile of the new data set:

OWNER indicates the user or group assigned as the owner of the data set profile.
ID is the access list of users or groups that are authorized to access the data set.
UACC gives universal access authority that is associated with the data set.
AUDIT|GLOBALAUDIT selects which access attempts are logged.
ERASE indicates that the data set when it is deleted (scratched).
LEVEL is the installation-defined level indicator.
DATA is installation-defined information.
WARNING indicates that an unauthorized access causes RACF to issue a warning message, but allows access to the data set.
SECLEVEL is the name of an installation-defined security level.

Exception: You can use the SECMODEL parameter to allocate both SMS-managed and non-SMS managed data sets. If SMS is not active, however, the system checks the syntax and then ignores the SECMODEL parameter.

For more information about RACF, see z/OS Security Server RACF Command Language Reference.

SPACE(quantity[,increment])

Allocates the amount of space for a new data set. If you omit this parameter, the system uses the IBM-supplied default value of SPACE(4,24) AVBLOCK (8192). However, your installation might have changed the default. For more information about default space, see z/OS MVS Programming: Authorized Assembler Services Guide.

To have the system determine the amount of space, include the AVGREC parameter in place of BLOCK, AVBLOCK, CYLINDERS, and TRACKS. To supply your own space value, define one of the following: BLOCK(value), BLKSIZE(value), AVBLOCK(value), CYLINDERS, or TRACKS. The amount of space requested is determined as follows:

BLOCK(value) or BLKSIZE(value): The BLOCK or BLKSIZE parameter's value is multiplied by the SPACE parameter's quantity.
AVBLOCK(value): The AVBLOCK parameter's value is multiplied by the SPACE parameter's quantity.
CYLINDERS: The SPACE parameter's quantity is given in cylinders.
TRACKS: The SPACE parameter's quantity is given in tracks.

Use SPACE for NEW and MOD data sets.

quantity: Allocates the initial number of units of space for a data set. For a partitioned data set, a directory quantity is not necessary.
increment: This is the number of units of space to be added to the data set each time the previously allocated space has been filled. You must provide the primary quantity along with the increment value.

BLOCK(value)

Shows the average length (in bytes) of the records written to the data set. The maximum block value used to determine space to be allocated is 65,535. The block value is the unit of space that is used by the SPACE parameter. A track or a cylinder on one device can represent a different amount of storage (number of bytes) from a track or a cylinder on another device. Determine the unit of space value from the:

Default value of (10 50) AVBLOCK(1000) if no space parameters (SPACE, AVBLOCK, BLOCK, CYLINDERS, or TRACKS) are given.
The BLOCK parameter.
The model data set, if the LIKE parameter is used and BLOCK, AVBLOCK, CYLINDERS, or TRACKS is not given.
The BLKSIZE parameter if BLOCK is not used.

AVBLOCK(value)

This shows only the average length (in bytes) of the records that are written to the data set.

CYLINDERS

Requests allocation in cylinders as the unit of space.

TRACKS

Requests allocation in tracks as the unit of space.

Exception: If you specify tracks for a VSAM data set, the space allocated will be contiguous. See z/OS DFSMS Using Data Sets “Optimizing Control Area Size,” for more information.

STORCLAS(storage-class-name)

For SMS-managed data sets: Gives the 1-to-8 character name of the storage class. When possible, allow STORCLAS to default through the ACS routines established by your storage administrator. Attributes assigned through storage class and the ACS routines replace storage attributes such as UNIT and VOLUME. If SMS is not active, the system checks the syntax and then ignores the STORCLAS parameter.

TRTCH(C|E|ET|T)

Selects the recording technique for 7-track tape as follows:

C: Data conversion with odd parity and no translation.
E: Even parity with no translation and no conversion.
ET: Even parity and no conversion. BCD to EBCDIC translation when reading, and EBCDIC to BCD translation when writing.
T: Odd parity and no conversion. BCD to EBCDIC translation when reading, and EBCDIC to BCD translation when writing.

The TRTCH and KEYLEN parameters are mutually exclusive.

UCOUNT(count)|PARALLEL

Shows device allocation.

UCOUNT(count): This allocates the maximum number of devices, where count is a value from 1-59.
If you do not use VOLUME and PRIVATE parameters and MAXVOL exceeds UCOUNT, the system removes no volumes when the mounted volumes have been used, causing abnormal termination of your job. If you use PRIVATE, the system removes one of the volumes and mounts another volume in its place to continue processing.
PARALLEL: Mounts one device for each volume given on the VOLUME parameter or in the catalog.

UNIT(type)

Defines the unit type to which a file or data set is to be allocated. You can list an installation-defined group name, a generic device type, or a specific device address. If you do not supply volume information (the system retrieves volume and unit information from a catalog), the unit type that is coded overrides the unit type from the catalog. This condition exists only if the coded type and class are the same as the cataloged type and class.

For VSAM data sets, use the AFF subparameter carefully. If the cluster components and the data and its index reside on unlike devices, the results of UNIT=AFF are unpredictable.

When you allocate a new SMS-managed data set, the system ignores the UNIT parameter. The system determines the UNIT and VOLUME from the storage class associated with the data set. Use UNIT only if you want to allocate a non-SMS-managed data set to a specific unit type.

If the storage administrator has set up a default unit under SMS regardless of whether the data set is SMS-managed, you do not have to use UNIT. If you do not, the system determines the default UNIT for both SMS-managed and non-SMS-managed data sets.

VOLUME(serial-list)

This is the serial number of an eligible direct access volume on which a new data set is to reside or on which an old data set is located. If you use VOLUME for an old data set, the data set must be on the specified volume for allocation to take place. If you do not include VOLUME, the system allocates new data sets to any eligible direct access volume. The UNIT information in your procedure entry in the user attribute data set (UADS) determines eligibility. You can use up to 255 volume serial numbers.

For VSAM data sets you must use this subparameter carefully. See the section that discusses DD parameters to avoid when processing VSAM data sets in z/OS MVS JCL User's Guide before using the VOLUME subparameters REF, volume-sequence-number, or volume-count.

When you allocate new SMS-managed data sets, you can let the ACS routines select the volume for you. The ACS routines assign your data set to a storage class containing attributes such as VOLUME and UNIT. You can allocate your data set to a specific volume only if your storage administrator has stated GUARANTEED SPACE=YES in the storage class assigned to your data set. The volume serial numbers you provide might then override the volume serial numbers used by SMS. If space is not available on the given volume, however, your request is not successful.

Abbreviation: VOL

VSEQ(vol-seq-no.)

This locates which volume (1-255) of a multivolume begins data set processing. This parameter corresponds to the volume sequence number on the VOLUME parameter in JCL. Use VSEQ only when the data set is a cataloged data set.