When an ILE program ends normally, the system returns control to the caller. The caller could be a workstation user or another program (such as the menu-handling program).
If an ILE program ends abnormally and the program was running in a different activation group than its caller, then the escape message CEE9901
Error message-id caused program to end.is issued and control is returned to the caller.
A CL program can monitor for this exception by using the Monitor Message (MONMSG) command. You can also monitor for exceptions in other ILE languages.
If the ILE program is running in the same activation group as its caller and it ends abnormally, then the message issued will depend on why the program ends. If it ends with a function check, then CPF9999 will be issued. If the exception is issued by an RPG procedure, then it will have a message prefix of RNX.
For more information on exception messages, see Exception Handling Overview.