With the exception of any specific details relating to the ROUTE option (see topic CMSG command options, ROUTE), all other information on the use of the following subsystems in message switching is given in the appropriate IBM subsystem guides:
The responses to 3270 family display devices are designed to fit on a single 40-character line of a Model 1 display. To provide more space for the response, the indicators that precede the response do not have the spaces between them that appear on non-3270 terminals.
Responses to the 3270 family display devices do not erase what is displayed on the screen and are displayed in the last 40 character positions of the line.
After a message-switching transaction has been started, you can press the CLEAR key if you want to continue from an empty screen. A CLEAR/CANCEL OR CONT xxxxx response is displayed, where xxxxx is either INPUT, ROUTE, or MSG. You can continue the transaction or, if you press the CLEAR key a second consecutive time, you can cancel the transaction. A better method of erasing the screen is to press the ERASE INPUT key, because this does not cause an interaction with the processor.
Because positions on the screen that are not keyed are not received, you can position and display data on the screen in various ways. For example, you can start each option on a new line of the display screen. You must include a comma between consecutive options. Also, if you want to start a new line within the message text you should enter a field mark character to indicate the end of the current line. All field mark characters within a message (including the first character of the message) are interpreted as NL characters (there is no corresponding key on 3270 family display devices) and cause correct positioning of the message on all other terminals.
The keyboard/printer unit of the 3767 is eligible for entering and receiving messages.
On a sequential (BSAM) terminal, the CMSG message-switching facility remains conversational until a message-switching transaction is completed or canceled. Variable conditions requiring a response, such as operators not being signed on, can be handled easily from an interactive terminal. These conditions, however, cannot always be anticipated, and the message-switching task continues reading input and issuing error messages until a valid response is received. It is possible that an entire sequential input stream could be consumed in such a process. You are advised to ensure that a CMSG CANCEL record appears in the sequential input following each message-switching transaction that could possibly require an unanticipated reply. This is strongly recommended following the final message-switching transaction.