Message identifiers include a prefix that identifies the source
of the message.
- Prefix
- Source
- ELM
- Logon manager messages
- IKT
- TSO/VTAM messages
- IST
- VTAM® network operator messages
- IUT
- MPC connection manager messages
- IVT
- Communications Storage Manager (CSM) messages
- USS
- Unformatted system services messages