IBM OS/390 manual System Interface and Macros, MVS Register Conventions

The selection of a particular option of MVS may require redesigning the application programs. In addition, a program logic change may also be forced by attempting to simulate a VSE function under MVS. Examples of these possibilities include multitasking, interrupt handling, and communication region accessing.

The input and output components of the linkage editors, the job control language, and linkage edit control statements necessary to build program structures are discussed in the publication DFSMS/MVS Program Management, SC26-4916.

VSE assembler language programs that are changed to MVS must add an initialization routine to meet MVS requirements. You should establish a standard for the entire installation that can be simply inserted into the assembler language source member before it is recompiled under MVS. For additional information on the MVS services and macro coding details, refer to the following publication:

∙OS/390 MVS Programming: Assembler Services Reference, GC28-1910.

For Data Management programming macro information, refer to:

∙

∙

DFSMS/MVS Using Data Sets, SC26-4922.

DFSMS/MVS Macro Instructions For Data Sets, SC26-4913.

Important

The macro functions and parameters described in this text may not be totally up-to-date. Macro facilities change over time. New macros and macro parameters become available with new releases of products. Therefore, you should always reference the appropriate macro manuals (listed above) for exact macro functions and applicable parameters. (Even though some macros may not be up-to-date, the techniques illustrated here should still be applicable.)

The next section highlights the services provided by the MVS supervisor and relates them to comparable ones provided by VSE. Information on VSAM macros is found in the section 13.2.5, ªVSAM Macrosº on page 290. Data Management macro comparisons are addressed in the section 13.2.6, ªData Management Macrosº on page 292.

13.2.1 System Interface and Macros

The functions of the VSE system interfaces and macros and their MVS equivalents are discussed in the following text.

MVS Register Conventions

Application program use of general purpose registers in MVS is restricted to registers 2 through 12. (Registers 0, 1, 13, 14 and 15 are used for special purposes by MVS - see next sections.) If VSE programs use other than registers 2-12 for application purposes, program register assignments may have to be changed.

268VSE to OS/390 Migration Workbook