The originating terminal

To send a message to the logical terminal that sent the input message, the program uses an I/O PCB. IMS puts the name of the logical terminal that sent the message in the I/O PCB when the program receives the message.

As a result, the program need not do anything to the I/O PCB before sending the message. If a program receives a message from a batch-oriented BMP or CPI Communications driven program, no logical terminal name is available to put into the I/O PCB. In these cases, the logical terminal name field contains blanks.