z/OS V1R6.0 DFSMS Access Method Services for Catalogs

ALLOCATEvvYou can use the LIKE parameter to allocate a data set with the same attributesas an existing (model) data set. The model data set must be a cataloged data set.You can override any of the model data set attributes by stating them in theALLOCATE command.You can identify a data set and explicitly describe its attributes.RestrictionsvvvIf the access method services job step contains either the SYSTSIN or SYSTSPRTDD statements, the ALLOCATE command is unsuccessful. Access methodservices allocates the SYSTSIN and SYSTSPRT DD statements to pass thecommand to the TMP and to retrieve any error messages that are issued. This isdone for every ALLOCATE command. Any TMP error messages appear in theSYSPRINT data set, and access method services prints a summary message toshow the final status of the command.The access method services ALLOCATE command is not supported if accessmethod services is called in the foreground of TSO or if Time Sharing OptionExtensions (TSO/E) Release 2 or later is not installed.You cannot use ALLOCATE if you have used the ATTACH macro to callIDCAMS from an application program. If you do, ALLOCATE fails with anATTACH return code.Allocating Storage Management Subsystem Managed Data SetsIf SMS is active, it can handle data set storage and management requirements foryou. The storage administrator defines SMS classes with ACS routines, whichassign classes to a new data set. When a storage administrator assigns a storageclass to a new data set, the data set becomes an SMS-managed data set. Data classand management class are optional for SMS-managed data sets. For information onwriting ACS routines, see z/OS DFSMSdfp Storage Administration Reference.Your storage administrator writes routines that assign SMS classes to a data set.The SMS classes are:vvvStorage class Contains performance and availability attributes you can use toselect a volume for a data set. You do not need to use the volume and unitparameters for a data set that is SMS-managed.Data class Contains the attributes related to the allocation of the data set, such asLRECL, RECFM, and SPACE. The data set attributes, if not specified on theALLOCATE statement, are derived from the model specified on LIKE, or fromthe data class. If the system cannot allocate the requested amount of space onthe eligible volumes in the selected storage group, SMS retries allocation with areduced space quantity. However, SMS will not do any retries, includingreduced space quantity, unless Space Constraint Relief =Y is specified. If the dataclass assigned to the data set allows space constraint relief, other limits can bebypassed.For a list of the attributes for a data class, see the description of the DATACLASparameter in this section.Management class Contains the attributes related to the migration and backup ofthe data set by DFSMShsm .Allocating Non-SMS Managed Data SetsYou can define the DATACLAS parameter to allocate non-SMS-managed data sets.Do not specify the STORCLAS and MGMTCLAS parameters.30 z/OS V1R6.0 DFSMS Access Method Services for Catalogs