A Mode is used to define the attributes of sessions used between a Local LU and a Remote LU.
If the default mode #INTER is not appropriate (because its settings are incompatible with the modes defined on the host system for the Remote LU, or perhaps because a larger number of sessions is required) then a new mode can be defined.
CCIAPPC uses a single APPC session for each CCI session between the client and the server (e.g. between the MFA client and Fileshare running on a mainframe). When CCIAPPC establishes a connection between the client and server the attributes of the Mode determine, amongst other things, the number of CCI sessions available between the Local LU and the Remote LU (APPLID in VTAM). Hence the Mode determines how many client sessions can be established using the same Local LU - Remote LU pairing.
The Maximum Session Limit and the Minimum Contention Winners values together determine how many sessions can be established by the Local LU (see below).
For example: if 10 client sessions are required, all using the same Local LU then the Mode session attributes might be:
Session Limits: Maximum = 20 Minimum contention winners = 15
Alternatively the same number of client sessions could be attained by using multiple Local LUs with the client sessions divided between these LUs.
When a connection is established between a Local LU and a Remote LU the Mode characteristics are negotiated. This means that it is possible that the partner system (e.g. mainframe) will reduce the session limits to values which it can support. This may mean that fewer client sessions than expected will be supported. Hence it is important that the Mode characteristics, as defined for both the Local and Remote LUs, are compatible.