Discontinue use of invalid REXX variables in z/OS UNIX syscalls

Description: Before z/OS V1R13, issuing z/OS UNIX syscalls with invalid REXX variables might not generate an error message. Starting in z/OS V1R13, error messages are issued.

Element or feature:

z/OS UNIX.

When change was introduced:

z/OS V1R13.

Applies to migration from:

z/OS V1R12.

Timing:

After the first IPL of z/OS V2R1.

Is the migration action required?

Yes. Using invalid REXX variables could cause problems that might not be noticed.

Target system hardware requirements:

None.

Target system software requirements:

None.

Other system (coexistence or fallback) requirements:

None.

Restrictions:

None.

System impacts:

None.

Related IBM Health Checker for z/OS check:

None.

Steps to take: If you have REXX programs with multiple syscalls that use the (rexx-variable) format of passing variables and do not check RETVAL and or ERRNO upon return, follow these steps.

Run these programs.
Fix parsing errors as they occur, replacing invalid REXX variables with valid ones. The error number will identify the invalid REXX variable. Note that REXX variable names cannot start with a digit or include arithmetic operators. For example, x*y is an invalid REXX variable.
- If the program produces a REXX parsing error, the error will be:
```
IRX0041I Error running ....... line xx:  ......
```
  This is a TSO REXX error message.
- If the program produces a z/OS UNIX syscall parsing error, the error code will be -21,-22,..., as described under the section "Returned from the SYSCALL environment" in the USS REXX documentation.

Reference information: See z/OS Using REXX and z/OS UNIX System Services for information about the error message.