Replying to the terminal

For a conversation to continue, the originating terminal must receive a response to each of its input messages. The person at the terminal cannot enter any more data to be processed (except IMS TM commands) until the response has been received at the terminal.

To continue the conversation, the program must respond to the originating terminal by issuing the required ISRT calls to send the output message to the terminal. To send a message to the originating terminal, the ISRT calls must reference either the TP PCB or an alternate response PCB. Use an alternate response PCB in a conversation when the terminal you are responding to has two components—for example, a printer and a punch—and you want to send the output message to a component that is separate from the component that sent the input message. If the program references an alternate response PCB, the PCB must be defined for the same physical terminal as the logical terminal that sent the input message.

The program can send only one output message to the terminal for each input message. Output messages can contain multiple segments, but the program cannot use the PURG call to send multiple output messages. If a conversational program issues a PURG call, IMS TM returns an AZ status code to the application program and does not process the call.