(1) For the IMS subsystem, the first 1 to 8 characters of the first segment of a message sent to IMS/VS. The transaction code identifies the application programme for which the message is intended.
(2) A 1- to 8-character alphameric code that invokes an IMS message processing program.
(3) In IMS and CICS, an alphanumeric code that calls an IMS message processing programme or a CICS transaction. Transaction codes have 4 characters in CICS and up to 8 characters in IMS.