How messages are routed in an IMSplex with shared queues

In an IMSplex with shared queues, IMS uses origin names and destination names registered with a coupling facility to route messages between front end and back end IMS systems.

Origin and destination names can be logical terminal names, transaction codes, or APPC or OTMA client names. You define static origin and destination names during system definition. You define in descriptor libraries or user exits the origin and destination names that are dynamic LTERMs, ETO terminals, or dynamic transactions. Origin and destination names for APPC or OTMA clients are sent, in the form of an 8-byte token, to IMS when an APPC or OTMA client allocates a conversation.

IMS registers transactions when they are started and a dependent region or an MSC link is started and ready to process messages. IMS registers LTERM names with the coupling facility when they are started or when they sign on and are ready to process messages. IMS registers APPC and OTMA tokens when an APPC or OTMA conversation is allocated. IMS deregisters APPC and OTMA tokens when the APPC or OTMA conversation is deallocated.

Messages carry these origin names and destination names in the message prefix. When an empty shared queue on a coupling facility receives a message from a front-end IMS system for a registered destination name, the coupling facility notifies all interested IMS systems that there are messages to process.