Regina REXX on Linux/zLinux ↔ z/OS TSO external functions: feasibility for low‑traffic workloads

Goal

Determine whether a low‑traffic REXX workload can be executed on Regina REXX running on Linux/zLinux while retaining access to the z/OS‑specific external functions (e.g., ADDRESS TSO, EXECIO) that many mainframe scripts depend on.

Constraints and uncertainty

• Regina REXX does not implement certain z/OS‑specific external functions, which may require script changes or wrapper code.
• IBM REXX compiler reduces per‑invocation CPU usage but incurs a separate product license and a compile step.
• Licensing terms for the IBM REXX compiler vary by release and workload metrics, affecting the cost‑benefit analysis.
• Performance gains from compilation depend on script complexity and invocation frequency; trivial scripts may see negligible savings.

Which z/OS‑specific external functions are missing in Regina REXX 4.0.0 and what effort is needed to replace or emulate them?

How much CPU time could be saved by using the IBM REXX compiler versus the interpreter for a workload that runs fewer than a defined number of invocations per day?

Does the expected licensing cost of the IBM REXX compiler outweigh the migration effort required to adapt scripts for Regina REXX?