Defining a workstation for terminal-response mode

You must understand the operation sequences of terminal response mode before defining a workstation to operate in terminal-response mode.

Less processor time is required for stations that operate in terminal response mode, and the controller application program that controls such a workstation might also be less complex.

The following considerations also apply:
  • Typical data collection applications cannot be performed from stations that operate in terminal-response mode. In this mode, a reply from the MPP is required for each transaction before IMS accepts another transaction. Waiting for this response extends the time of the data entry process.
  • IMS does not send a response to an input message until the output reply is available. Thus, when the response is returned, it indicates that the input has been processed and the application has reached a sync point.
  • While a workstation is in terminal-response mode, IMS does not attempt to obtain any more input from that station. Master terminal operator intervention is required if an error prevents creation or transmission of a reply. Some conditions can prevent a reply being sent to the workstation. These include:
    • The LTERM stopped.
    • IMS was unable to schedule an MPP (database stopped, MPP stopped).
    • An MPP logic error caused no reply to be returned except for EMH (expedited message handler), which generates a zero-length reply.

    If any of these conditions occurs, the workstation is temporarily inoperative. Before the workstation can be used again, the master terminal operator must diagnose and correct the error.

  • A response message remaining on the IMS output queue or inserted by the user-MPP after session termination is re-sent after initiation of the next session. If the BID option is specified, this message is preceded by the VTAM® BID command. Both the begin-bracket and end-bracket indicators are sent with the message.

System analysts must evaluate these factors for their own system application programs and operating environment.