Field	Use
TXn_ID / Txn_ID	Primary identifier for detecting whether the same transaction message was already processed.
traceid_lifecycle	Helps identify related lifecycle messages.
Traceid_Message	Helps identify the specific message instance.
Trans_link	Supports transaction linking and matching.
Ret_Ref_No_DE37	Retrieval reference number.
Auth_Code_DE38	Authorization code.
SendingAttemptCount	May indicate repeated delivery attempts.