VSAM ignores parameters for defining tape data sets; data-set sequence numbers, NSl, Nl, BlP, and Al. You cannot use the parameters for a sequential data set (DATA, SYSOUT, and *) for specifying a VSAM data set. DD names that are invalid for VSAM data sets are: JOBlIB, STEPlIB, SYSABENO, SYSUOUMP, and SYSCHK.
OD parameters that are invalid are: UCS, QNAME, OYNAM, TERM, and the forms of DSNAME for ISAM, PAM (partioned access method), and generation data groups. VSAM does not allow for temporary data sets or concatenated data sets.
CODING A DO STATEMENT FOR A CATALOG
The master catalog is always available, without specifying it via JCL. You make other catalogs available by describing them
in DD statements with special names for a job (JOBCAT) or a job step (STEPCAT), or by using special naming conventions where the high-level qualifier of the data set name is also the name of the user catalog. You describe a catalog sufficiently by giving
its data set name and specifying DISP=SHR. A catalog can be either a JOBCAT or a STEPCAT catalog. If both JOBCAT and
STEPCAT catalogs are specified, the STEPCAT catalog is available for the step for which it is specified, and the JOBCAT catalog is available for all steps within the job. VSAM uses a data set's name as a search argument to search a catalog. You can minimize the use of JOBCAT and STEPCAT DD statements for your jobs when you name your data set with a qualified entryname whose first qualifier is the name or alias of the catalog in which the data set is defined. When the catalog is not
identified with a DD statement, the scheduler searches the master catalog for the data set's entryname. If the entryname
is not found, the system uses the entryname's first qualifier as a search argument and attempts to locate either a catalog entry or a catalog's alias entry in the master catalog. If the system finds a catalog or alias entry whose name is the same as the data set name's first qualifier, the operating system searches that catalog for the data set's catalog record, using the data set's full entryname.
If no catalog is indicated or if the definition is not found in the catalog(s) that are indicated, the master catalog is assumed to contain the definition of the data set described in a DD statement. A catalog is specified either for all the steps of a job or for a particular step. To specify a job catalog, place a DD statement with the ddname JOBCAT before the first EXEC
statement after the JOB statement and after a JOBLIB statement, if any:
//EXAMPLE //JOBLIB //JOBCAT
/ /
JOB DD DD EXEC
DSNAME=USER.LIB,DISP=SHR
DSNAME=usercatalogname,DISP=SHR
To specify a job step catalog, place a DD statement with the ddname STEPCAT after the EXEC statement of the step:
//STEPI EXEC . . .
//STEPCAT DD DSNAME=usercatalogname,DISP=SHR
The order in which catalogs are searched when an existing entry is to be located is:
• If a catalog is specified in a CATALOG parameter of the access method services DEFINE command, only that catalog is
searched.
• Any catalog(s) specified in the current job step (STEPCAT) or, if none is specified for the job step, any user
catalog(s) specified for the current job (JOBCAT). If more than one catalog is specified for the job step or job, the job-step or job catalogs are searched in order of
concatenation. For information of the search order, see Access Method Services Reference.
• If the entry is not found and the entry's name is a qualified name and the first qualifier (the first one to eight characters before any period) is the same as the name or alias of a catalog or the alias of an OS CVOL, that catalog or OS CVOL is searched; otherwise, the master catalog is searched.
RESTRICTION: OS CVOls are not searched (1) when an existing data set is to be deleted except when the data set to be deleted, is a non-VSAM data set, or (2) when an existing data set is to be altered.
CODING THE AMP PARAMETER
VSAM has one additional JCl parameter of its own: AMP. The AMP parameter takes effect when the data set defined by the DD statement is opened. It has subparameters for:
• Overriding operands specified by way of the ACB, EXlST, and GENCB macros
• Supplying operands missing from the ACB or GENCS macro
• Indicating checkpoint/restart options
• Indicating options when using ISAM macros to process a key-sequenced data set
• Indicating that the data set is a VSAM data set when you specify unit and volume information or DUMMY in the DD statement
• Indicating that you want VSAM to supply storage dumps of the access method control block(s) that identify this DD
statement
The AMP parameter takes effect when the data set defined by the DD statement is opened.
The format of the AMP parameter is:
/ /
...
DO ••• AMP=(['AMORG'][,'BUFND=number']
[,'BUFNI=number']
[,'BUFSP=number']
[,'CROPS={RCKINCKINREINRC)']
[,'OPTCD={YTIIIl)'l [,'RECFM={FIFSIVIVB)']
[,'STRNO=number']
[,'SYNAD=modulename'l [,'TRACE']])
where:
AMORG
specifies that the DD statement defines a VSAM data set.
When you specify unit and volume information for a DCS (through the ISAM interface program) or DUMMY in the DD statement, you must specify AMORG. Under these conditions, the system doesn't have to search a catalog to find out what volume(s) are required, and therefore doesn't know that the DD statement defines a VSAM data set. You never have to specify unit and volume information, unless you want to mount a subset of the volumes on which the data set is stored, or want to defer mounting.
BUFND=number
specifies the number of data buffers.
BUFNI=number
specifies the number of index buffers.
BUFSP=number
specifies that one or more of these values is to override whatever was specified in the ACB or GENCS macro, or that one or more of these values is to be provided if not previously specified. For further information on BUFND, BUFNI, and BUFSP, see VSAM Re~ence.