OTMA program-to-program switch processing

Two types of message switch occur in OTMA: commit-then-send, and send-then-commit.

For OTMA commit-then-send input messages (also called asynchronous or commit mode 0 messages), the program switch always results in another commit mode 0 (CM0) message. For OTMA send-then-commit input messages (also called synchronous or commit mode 1 messages), the program switch results vary, depending on whether:
  • there is an ISRT call to the I/O PCB
  • an express PCB is used for the switch
  • there is a switch to multiple programs
  • the IMS start-up parameter OTMAASY=Y or OTMAASY=S is specified
  • the transaction is protected

A P2P switch for a commit mode 1 (CM1) input message, therefore, could be another CM1 message, a DFS2082 message, or a CM0 message. In addition, some OTMA clients, for example IBM® MQ, can accept a CM0 output message for a CM1 input message; others, however, may not.

The following topics provide usage scenarios for different send-then-commit message switches.