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

Chapter 4. ALLOCATEAccess method services identifies the verb name ALLOCATE and attaches theterminal monitor program (TMP) that runs Time Sharing Option (TSO) commandsin the background. The ALLOCATE command should be used only to allocate newdata sets to the job step. If you use ALLOCATE through access method services foranything else (the handling of SYSOUT data sets, for example), you can getunpredictable results. Refer to z/OS TSO/E Programming Guide for additionalinformation on using this command. Table 2 on page 31 separates the parametersto that you should use under access method services from the parameters thatcause unpredictable results.When ALLOCATE is used, the data set is allocated to the job step. If your jobcontains multiple allocations, you might need to use the DYNAMNBR parameteron the job control language (JCL) EXEC statement. DYNAMNBR establishes acontrol limit used by TMP when allocating a data set. The control limit is thenumber of data definition (DD) statements that are coded plus the value coded inDYNAMNBR. If you do not use DYNAMNBR, the system sets it to 0 (the default).If you code DYNAMNBR incorrectly, the system uses the default and issues a JCLwarning message. See z/OS MVS JCL User’s Guide for a description of how to codethe DYNAMNBR parameter. For an example illustrating the use of DYNAMNBR,see “Allocate a Data Set Using SMS Class Specifications: Example 1” on page 48.When you use the ALLOCATE command within access services, you must followthe data set naming conventions of TSO when the TMP is run in batch mode. Thatis:vIf the data set name is not in quotation marks and a USER parameter is given inthe JCL, the value in the USER parameter is prefixed to all data set names givenby ALLOCATE.v If the USER parameter is not in the JCL, no prefix is added to any data set namegiven by ALLOCATE.For information about the naming conventions of TSO and other considerationswhen you use access method services commands from a TSO background job, seez/OS TSO/E User’s Guide. For information about the USER parameter and itsResource Access Control Facility (RACF) requirements, see z/OS MVS JCL Reference.You can use the ALLOCATE command to define data set attributes in severalways:vYou can use the Storage Management Subsystem (SMS) parameters STORCLAS,MGMTCLAS, and DATACLAS. You can either define these parameters explicitly,or you can let them to use the parameters assigned by the ACS routines thatyour storage administrator defines. Contact your storage administrator for aboutstorage administration policies and about how the ACS routines might apply.You cannot override attributes that the STORCLAS and MGMTCLAS parametersassign. You can override attributes that the DATACLAS parameter assigns. Forexample, if you use both the DATACLAS parameter and the SPACE parameter,SMS assigns all the attributes defined in the DATACLAS, but uses the valuesyou defined in the SPACE parameter when allocating the data set.© Copyright IBM Corp. 1973, 2004 29