For an SMS-managed data set, SMS obtains information about the
device to be used for the data set based on the storage class assigned
for the data set.
In many cases, the device used by the storage class that an ACS
routine selects is sufficient for the data sets you create with DD
statements.
You can, however, specify the name of a storage class on the STORCLAS
parameter for a new SMS-managed data set. (Note that an ACS routine
can override the storage class that you specify.)
The storage administrator at your installation defines the names
of storage classes and their attributes. To view a list of storage
class names and their attributes, use Interactive Storage Management
Facility (ISMF).
To let an ACS routine select a storage class for a new data set,
omit the STORCLAS parameter; for example:
//DD5 DD DSNAME=DESIGNA.PGM,DISP=(NEW,KEEP)
To specify a specific storage class for a new data set, code
the STORCLAS parameter; for example:
//DD6 DD DSNAME=DESIGNB.PGM,STORCLAS=STOR55,DISP=(NEW,KEEP)
The system catalogs new permanent system-managed DASD data sets at allocation. The system
catalogs data sets on a system-managed tape volume during unallocation processing, according to DISP parameters
on DD statements.
To retrieve an existing data set, you do not need to code the STORCLAS
parameter; for example:
//DD7 DD DSNAME=DESIGNB.PGM,DISP=MOD
If you specify the UNIT parameter for an SMS-managed data set,
the system generally ignores the parameter. There are, however, several
cases when the system uses the information specified on the UNIT parameter:
- For data sets on a system-managed tape volume, the system ignores
the device type, device number, and group name subparameters of the
UNIT parameter but honors all its other subparameters. For example,
it uses the unit-count subparameter to allocate the specified number
of units. However, if SMSHONOR is coded, the device
number or group name subparameter specified is honored, and the system
attempts to allocate to the specified unit. For further information
see the z/OS MVS JCL Reference information.
- For system-managed DASD data sets, the system honors the unit-count subparameter but
ignores all other subparameters on the UNIT parameter. For further
information see the z/OS MVS JCL Reference information.