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When a Logical Unit (LU) starts a session (LOGON), it provides a set of parameters that identify the LU to the VTAM application. The parameters include screen size; ability to display extended data stream (such as color or highlights); and other parameters that determine session protocol. Parameters describing the screen in a VTAM session are grouped into a LOGMODE entry. LOGMODE entries are, in turn, stored in LOGMODE tables.
KOA emulates different types of terminals according to user specifications. The KOA language provides commands such as SCREENSIZE and COLOR for automatic selection of LOGMODE entries from a predefined list (which is created during KOA installation). Four different terminal sizes are currently available, and each size may or may not support extended data stream.
You can override the KOA-selected LOGMODE by specifying the LOGMODE parameter of command LOGON. In this case, LOGMODE (and not the commands SCREENSIZE and COLOR) determines terminal characteristics.
Certain online systems (such as IMS/DC and, optionally, CICS) require that LUs be predefined, and that they be stored in internal tables. Each definition in the table contains the name and characteristic for that LU. When logging on to these online systems, the LOGMODE information is ignored and the predefined values are used. In this case, the SCREENSIZE, COLOR and LOGMODE commands and parameters have no effect.
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