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

Appendix D. Invoking Access Method Services from YourProgramThis appendix is intended to help you to invoke access method services from yourprogram.Access method services is invoked by your program through the ATTACH, LINK,or LOAD and CALL macro instructions.The dynamic invocation of access method services enables respecification ofselected processor defaults as well as the ability to manage input/outputoperations for selected data sets.A processing program invokes access method services with the ATTACH, LINK,LOAD, and CALL macros. Before issuing the invoking macro, however, theprogram must initialize the appropriate register and operand list contents.The register contents follow standard linkage conventions:vvvregister 1 contains the address of the argument listregister 13 contains the address of a save arearegister 14 contains the address of the return pointv register 15 contains the address of the entry point IDCAMS in access methodservices.IDCAMS only supports 24-bit virtual addresses that are passed in argument lists,control blocks, buffers, and user exit routines, and USER EXIT can only be called inAMODE24. However, IDCAMS can be called in 31-bit mode but will switch to24-bit mode and then return to the calling program in the caller’s mode.The contents of the operand list are described in Figure 31 on page 425. Refer to“Authorized Program Facility” in z/OS DFSMS: Managing Catalogs for informationon manipulating sensitive data in a secured environment.Authorized Program Facility (APF)Invoking Macro InstructionsAny program calling IDCAMS to issue a DCOLLECT or SHCDS command mustbe APF authorized or these commands will terminate. When IDCAMS is calledfrom a program to issue the ALLOCATE command to allocate a SMS-manageddata set, that program must be in an APF authorized program. For information onAPF authorization, see z/OS DFSMS: Managing Catalogs. For information on usingAPF, see z/OS MVS JCL User’s Guide.The following descriptions of the invoking macro instructions are related toFigure 31, which describes the argument lists referenced by the invoking macros.LINK or ATTACH Macro InstructionAccess method services is invoked through either the LINK or the ATTACH macroinstruction.© Copyright IBM Corp. 1973, 2004 421