Understanding an EXCP terminal session
An EXCP terminal is a 3270 display station that is channel-attached to your host through a non-SNA control unit.
Therefore, the terminal is directly accessed through a MainView Alternate Access EXCP session by using channel programming rather than being connected through your VTAM network.
A directly connected terminal can communicate with the host by using the EXCP access method. This type of low-level communication requires the user session to manage the communication protocols and does not support any form of user services, such as logon panels. Without logon support, an EXCP session must be initialized by an operator START command. (For MainView Alternate Access, this task is accomplished by starting a TAS for the terminal’s unit address.)
However, when you use a terminal that is connected through your VTAM network, VTAM manages the communication protocols, logon functions, and other services for your user session. For this reason, non-SNA terminals are typically connected to the VTAM network so that users can log on or perform other functions without requiring operator assistance. Usually, you can tell whether your terminal is channel-attached through a non-SNA local control unit by the presence of an A character in the second column of the status line on the terminal.