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Status Delivered
Workspace IBM i
Categories Languages - RPG
Created by Guest
Created on Aug 9, 2021

Extend ON-ERROR to accept message codes

In our codebase, we use a lot of user-defined message codes in *ESCAPE messages for our exception handling. We combine these with RPG's MONITOR op-code to trap the errors and, if possible, handle them.

Identification of the last exception message code is not an issue. What is currently missing is an elegant mechanism to trap a specific subset of error codes.

Here is a simplified example of how our code might look currently:

lastError = getLastException();
if lastError = 'USR0001';
// Remedial action
// Send new escape message

Since ON-ERROR does not allow us to distinguish between different message codes we must capture all exception messages in a general ON-ERROR block. The problem here is that when we hit an exception we don't care about, we have the choice of either:
- leaving the handled message in the job log, adding a lot of noise; or
- removing the message, and losing the context of the original error.

If we could change ON-ERROR to only execute for particular message codes, we could leave other unexpected exceptions unhandled to percolate up the call stack.

If we could add handlers for specific message codes, RPG's native error handling would also more closely resemble exception handling features found in other languages e.g. Java, Python.

RFE 135394, to control job log output, would nicely complement this to bring rich exception handling directly into the RPG language.

Use Case:

An example could look like this:

on-error 'USR0001';
// Remedial action A
on-error 'USR0002' : 'USR0003';
// Remedial action B
on-error 'USR*';
// Remedial action C, for all other USRxxxx messages

// Exceptions with message prefixes other than 'USR' would percolate up the call stack

Another op-code could be used (ON-EXCEPTION?) if there is too much ambiguity with the existing ON-ERROR behaviour.

Idea priority Medium
  • Guest
    May 3, 2022
    IBM believes that the request described has been solved and is available with PTFs for 7.3 and 7.4 with the new ON-EXCP operation code for a MONITOR group. See

    7.3 PTF for the RPG compiler: 5770WDS SI79717
    7.3 PTF for the RPG runtime: 5770SS1 SI79656

    7.4 PTF for the RPG compiler: 5770WDS SI79711
    7.4 PTF fr the RPG compiler with TGTRLS(V7R3M0):: 5770WDS SI79719
    7.4 PTF for the RPG runtime: 5770SS1 SI79655

    Note: You need the PTF for the RPG runtime on any system where you run a program with the ON-EXCP operation code.
  • Guest
    Sep 28, 2021

    The CAAC has reviewed this requirement and recommends that IBM view this as a high priority requirement that is important to be addressed. For anyone who comes to the IBM i platform and looks at RPG, if they are used to a different language, they would definitely consider this to be a big gap. Long-time RPG programmers would appreciate the greater flexibility.

    Background: The COMMON Americas Advisory Council (CAAC) members have a broad range of experience in working with small and medium-sized IBM i customers. CAAC has a key role in working with IBM i development to help assess the value and impact of individual RFEs on the broader IBM i community, and has therefore reviewed your RFE.

    For more information about CAAC, see

    Nancy Uthke-Schmucki - CAAC Program Manager

  • Guest
    Aug 31, 2021

    IBM will use this request as input to planning but no commitment is made or implied. This request will be updated in the future if IBM implements it. IBM will use votes and comments from others in the community to help prioritize this request.

    If IBM implements this, it will most likely use the suggestion to add another opcode, such as ON-EXCEPTION.

    Regarding the suggestion in the comments by Jon Paris, to add a way to "throw" an exception with a particular status code, please open a separate RFE for that.

  • Guest
    Aug 10, 2021

    To match the try/catch type error handling methods of Java etc. perhaps a solution in part could be to allow RPG to throw specific error codes which could be caught by Monitor. There are a wide range of status codes that RPG does not currently assign and could be designated as available to the user.