MSC and standard IMS application programs

When an APPC application program enters an IMS transaction that executes on a remote IMS, an LU 6.2 conversation is established between the APPC application program and the local IMS.

The local IMS is considered the partner LU of the LU 6.2 conversation. The transaction is then queued on the remote transaction queue of the local IMS. From this point on, the transaction goes through normal MSC processing. After the remote IMS executes the transaction, the output is returned to the local IMS, and is then delivered to the originating LU 6.2 application program.

The originating (local) IMS provides the following services:
  • Receives incoming transaction from an LU 6.2 application program
  • Calls the Input Message Routing exit routine
  • Queues the transaction to its remote transaction queue
  • Sends the transaction across the MSC link
  • Receives the transaction response
  • Sends either synchronous or asynchronous output to an LU 6.2 application program
The remote IMS provides the following services for the remote standard application program:
  • Receives the incoming transaction from the partner IMS (originating or intermediate IMS) over the MSC link
  • Schedules transactions into dependent regions
  • Commits database changes at sync point
  • Provides necessary transaction recoverability
  • Provides necessary transaction rollback and retry
  • Keeps transaction output on the IMS message queue until the transmission is successful
  • Returns the transaction output to the local IMS over the MSC link

Restriction:  MSC is not supported if the originating LU 6.2 conversation is allocated with SYNCLVL=SYNCPT.