IBM i Message ID Lookup

How IBM i Message IDs Are Structured

Every IBM i (AS/400, iSeries) message has a seven-character ID: a two-to-four letter prefix followed by four hexadecimal digits, like CPF4131, MCH1202, or SQL0204. The prefix is the important part. It tells you which part of the system raised the message and which message file holds its full description. The four digits identify the specific message within that prefix's range.

What the Prefix Tells You

CPF messages come from the operating system control program (message file QCPFMSG) and are usually escape messages that end a step; CPC, CPD, and CPI are the completion, diagnostic, and informational variants. MCH messages are machine-interface exceptions from the Licensed Internal Code, the layer below the operating system, and point to low-level problems like decimal-data errors or invalid pointers. RNX and RNQ are ILE RPG runtime exceptions and inquiries (QRNXMSG), SQL messages map to Db2 for i SQLCODEs (QSQLMSG), and CEE messages come from the ILE common runtime (QCEEMSG). Knowing the prefix often tells you where to start before you read a single line of message text.

Reading the Full Message on Your System

IBM does not publish every message description on the web, and the text can differ slightly by release and PTF level, so the authoritative source is always your own system. This tool builds the exact DSPMSGD command for the ID you enter (for example DSPMSGD RANGE(CPF4131) MSGF(QCPFMSG)), which shows the message text, the cause, and the recovery as IBM ships them on your machine. For common messages it also adds a plain-language explanation and the first things I would check.

When a Message Keeps Coming Back

A message in a job log is rarely the whole story; the fix usually lives in the program or the data behind it. I work on IBM i and AS/400 systems, from modernization to integration and ongoing support. Have a recurring message you cannot pin down? Ask James.