Field	How your system should use it
MTID	Identifies the high-level message type.
Txn_Type	Identifies the transaction category or lifecycle event.
Txn_Stat_Code	Provides transaction status context when present.
Txn_ID / TXn_ID	Identifies the transaction message and supports duplicate detection.
traceid_lifecycle	Helps link related lifecycle messages.
Traceid_Message	Identifies the specific message instance.
Traceid_Original	References the original message, when present.
Trans_link	Supports transaction linking and matching.
Auth_Code_DE38	Useful for matching later messages to the original authorization.
Ret_Ref_No_DE37	Retrieval reference number used for matching and investigation.
CutOffId	Identifies cut-off messages and supports cut-off duplicate detection.