Running the REXX program

Before calling a TSO/E REXX service to run the program, ensure that file descriptors 0, 1, and 2 are open. The REXX program will fail if it attempts a PARSE EXTERNAL, EXECIO, or SAY and that function fails.

After the REXX environment is established, the program can call either the IRXJCL or the IRXEXEC TSO/E REXX service to run the REXX program.

If the IRXJCL service is used, the name of the REXX program is the first word of the IRXJCL parameter string. It is limited to 8 characters.
If you request the IRXEXEC service to load the program, you must provide the name of the REXX program in the member field of the EXECBLK. Set the DDNAME field to spaces. This also limits the name of the REXX program to 8 characters. Names longer than 8 characters can be supported with additional programming effort. You would need to preload the program and build an INSTBLK instead of an EXECBLK for the IRXEXEC call. If the REXX program is compiled in CEXEC format, load it as a single-record program.
If the name of the REXX program does not contain a slash (/), the PATH environment variable is used to locate the program.

The current REXX environment must be the z/OS UNIX REXX environment. You cannot pass the environment to be used in Register 0.

When the REXX program is being loaded, the IRXEXEC or the IRXJCL service uses one file descriptor to open the file, read it, and close it. If no file descriptor is available because the maximum number of file descriptors are already open, the program cannot be loaded.