1. Open Configuration Manager -> Expert Interface -> Automation -> Session Definition Sets
2. Scroll down to the Function Windows section. You will that the Notification Messages and OPS/MVS Messages function windows have an 'X' mark.
3. Select the Notification Messages function window and right-click.
4. Select 'enable' from the context menu. You will then see an '*' mark next to this session.
5. Right click this same item again, and select "apply changes to runtime."
6. Apply steps 3-5 above to the OPS/MVS messages function window.
7. Now you can recall the command to invoke your REXX program and you should not see these error messages.