IMS Adapter for REXX reference

This product does not compete with DFSDDLT0 but is used as an adjunct. The IMS adapter for REXX provides an application programming environment for prototyping or writing low-volume transaction programs.

The REXX environment executing under IMS has the same abilities and restrictions as those documented in the z/OS® TSO/E REXX Reference. These few restrictions pertain to the absence of the TSO, ISPEXEC, and ISREDIT environments, and to the absence of TSO-specific functions such as LISTDS. You can add your own external functions to the environment as documented in the z/OS TSO/E REXX Reference.

IMS calls the REXX EXEC using IRXJCL. When this method is used, Return Code 20 (RC20) is a restricted return code. Return Code 20 is returned to the caller of IRXJCL when processing was not successful, and the EXEC was not processed.

A REXX EXEC runs as an IMS application and has characteristics similar to other IMS-supported programming languages, such as COBOL. Programming language usage (REXX and other supported languages) can be mixed in MPP regions. For example, a COBOL transaction can be executed after a REXX transaction is completed, or vice versa.

The advantages of REXX are:

• REXX is an easy-to-use interpretive language.
• REXX does not require a special PSB generation to add an EXEC and run it because EXECs can run under a standard PSB (IVPREXX or one that is established by the user).
• The REXX interface supports DL/I calls and provides these functions:
  • Call tracing of DL/I calls, status, and parameters
  • Inquiry of last DL/I call
  • Extensive data mapping
  • PCB specification by name or offset
  • Obtaining and releasing storage
  • Messaging through WTO, WTP, WTL, and WTOR

The following system environment conditions are necessary to run REXX EXECs:

• DFSREXX0 and DFSREXX1 must be in a load library accessible to your IMS dependent or batch region; for example, STEPLIB.
• DFSREXX0 is stand-alone and must have the RENT option specified.
• DFSREXX1 must be bound with DFSLI000 and DFSCPIR0 (for SRRCMIT and SRRBACK) and optionally, DFSREXXU. The options must be REUS, not RENT.
• IVPREXX (copy of DFSREXX0 program) must be installed as an IMS transaction program. IVP (Installation Verification Program) installs the program.
• The PSB must be defined as assembler language or COBOL.
• SYSEXEC DD points to a list of data sets containing the REXX EXECs that will be run in IMS. You must put this DD in your IMS dependent or batch region JCL.
• SYSTSPRT DD is used for REXX output, for example tracing, errors, and SAY instructions. SYSTSPRT DD is usually allocated as SYSOUT=A or another class, depending on installation, and must be put in the IMS dependent or batch region JCL.
• SYSTSIN DD is used for REXX input because no console exists in an IMS dependent region, as under TSO. The REXX PULL statement is the most common use of SYSTSIN.

Related reading: For more information on SYSTSPRT and SYSTSIN, see z/OS TSO/E REXX Reference.