DYNAM Command

Syntax: How to Manipulate Data Sets Under z/OS

DYNAM subcommand operand [operand]...

where:

subcommand

Required. Is one of the following operations:

ALLOCATE ALLOC ALLO	Allocates a data set. A wide variety of allocation options is supported.
CONCAT CONC	Concatenates data sets.
FREE	Frees data sets specified by ddnames or dsnames. Each name may contain wildcard characters.
CLOSE CLO	Closes data sets. Useful when the data sets cannot be freed because they are open. The command has the same syntax as DYNAM FREE above.
COPY	Copies an entire data set or selected PDS members. The command has powerful features such as record format conversion, either automatic or controlled by options.
COPYDD	Copies data between z/OS data sets and/or HiperFOCUS files. DYNAM COPY has been enhanced to handle all functions offered by COPYDD, and is recommended for use instead of COPYDD.
DELETE DEL	Deletes an entire data set or selected PDS members.
RENAME REN	Renames an entire data set or selected PDS members.
SUBMIT SUB	Submits z/OS jobs.
COMPRESS COMP	Compresses partitioned data sets (PDSs).

operand: May be a keyword, a keyword followed by its parameter, or a parameter without a keyword.

The following rules apply to the DYNAM command:

The subcommand name, keywords, and parameters are separated with one or more blanks. Keywords are coded in free format.
A parameter may be a list of subparameters (for example, VOLUME for a multi-volume data set). Subparameters in the list should be separated with commas. For blanks between subparameters (with or without the comma), enclose the entire list in parentheses. For example:
```
A,B (A,B) (A B) (A, B) (A,B C, D)
```
DYNAM commands may span several lines. To do so, enter a hyphen (-) at the end of each line to be continued. In concatenating the lines, blanks after the hyphen and leading blanks from the next line are removed. Blanks before the hyphen are removed if they are preceded with a comma. The total length of a DYNAM command may not exceed 2048 characters.
Most keywords may be truncated up to the shortest unambiguous length. The commonly used abbreviations are fixed. It is important to note that the unique truncation of a keyword may not always be valid as new keywords are added. Using the full keyword in files and using truncations interactively is recommended.
Fixed abbreviations are listed in the following syntax descriptions. For example, DDNAME may be abbreviated as DD, DDN, DDNA, DDNAM, or DDNAME.
Certain keywords have synonyms. For example, the keywords FILENAME and DDNAME are synonyms, and so are DATASET and DSNAME.
As in TSO, a data set name can be enclosed in single quotation marks. Prefix substitution is not supported; only the fully qualified data set names should be specified.
Some DYNAM commands accept either the ddname or data set name (dsname) as the same parameter. In such cases, the parameter is considered a ddname if it is not longer than 8 bytes, does not contain periods (.), and is not enclosed in single quotation marks. Otherwise, the parameter is considered a data set name. Thus, to specify an unqualified data set name, enclose it in single quotation marks.
Dialogue Manager variables can be used in a DYNAM command, in which case the variable value is substituted at run time. If a variable is used as part of a data set name, it may need to be followed by extra period characters (.) in order to be substituted correctly. For example, in the following DYNAM command, three periods are required. The first period ends the variable name. If there were only a second period, it would be considered an indexed variable, and no period would be inserted in the string. The third period indicates that one period should be inserted into the string after the variable name:
```
-SET &OUT_NAME = CAR ;
DYNAM ALLOC F CAR DA USER1.&OUT_NAME...FOCUS SHR REU
```
The resulting string is:
```
DYNAM ALLOC F CAR DA USER1.CAR.FOCUS SHR REU
```

The DYNAM command and its subcommands, except for COMPRESS and CLOSE, are available from the DYNAM Utilities Menu. Additional allocations for the menu are not required. Private applications may be included on the primary menu. To access the menu, enter the command:

EX DYMENU

Use of Data Sets

z/OS obtains a lock for any allocated data set name: a shared lock for those specified as SHR; an exclusive lock for OLD, NEW, or MOD.

Although data sets can be allocated more than once in a job step, only one type of lock may be obtained. For example, if the data set is allocated as SHR and is then allocated as OLD in the same step, the z/OS lock changes from shared to exclusive, and the data set will not be available for use by other jobs until all allocations in this job are freed.

In addition, a z/OS exclusive lock is not sufficient in multi-user environments, such as FOCUS MSO. If one user were to allocate a data set as OLD, z/OS would allow another user to allocate it as OLD also, because both requests occur in the same job step. This can cause data set corruption due to simultaneous updating.

In order to alleviate these issues, the DYNAM commands that manipulate data sets use an improved locking mechanism, similar to that implemented in ISPF:

Any output PDS is allocated by DYNAM (or preallocated by the user) as SHR. This avoids exclusive z/OS locking, which lasts until all data set allocations are free.
To protect from simultaneous updating, DYNAM obtains an exclusive lock as used by ISPF (and other programs, including LINKEDIT), but only during the actual update time. This lock controls access to the data set between users, even from within the same job step.
Note: The DYNAM locking mechanism protects from simultaneous updating and possible corruption of data, but does not protect from updating and simultaneous reading. For example, it is possible to continue to read a PDS member recently deleted by another user.

ALLOCATE Subcommand

How to:

Allocate a Data Set With the ALLOCATE Subcommand

The DYNAM ALLOCATE command allocates a data set.

APPEND	Adds the input to the end of the existing data, if the output is a sequential data set.
FORCE	Copies input DCB attributes (RECFM, BLKSIZE, LRECL and KEYLEN) to the output data set. By default, only missing values are assigned. Note: Do not use FORCE to change the LRECL of one member of an existing PDS as doing so may potentially destroy the PDS.
KEYMOD	Allows key modification according to input/output KEYLEN: truncation or padding with binary zeros.
REPLACE	Replaces all output members matching the selected member names.
TRUNCATE	Allows truncation of input records that are longer than the output record length. Since trailing blanks are truncated automatically when RECFM is different, the keyword is used either to cut records of the same format or to cut non-blank data.