Before traffic can flow on an intersystem session, the session must be established, or bound. CICS® can be either the primary (BIND sender) or secondary (BIND receiver) in an intersystem session, and can be either the contention winner or the contention loser. The contention winner in an LU-LU session is the LU that is permitted to begin a conversation at any time. The contention loser is the LU that must use an SNA BID command (LUTYPE6.1) or LUSTATUS command (APPC) to request permission to begin a conversation.
The number of contention-winning and contention-losing sessions required on a link to a particular remote system can be specified by the system programmer.
For LUTYPE6.1 sessions, CICS always binds as a contention loser.
For APPC links, the number of contention-winning sessions is specified when the link is defined. (See Defining APPC links.) The contention-winning sessions are normally bound by CICS, but CICS also accepts bind requests from the remote system for these sessions.
Normally, the contention-losing sessions are bound by the remote system. However, CICS can also bind contention-losing sessions if the remote system is incapable of sending bind requests.
A single session to an APPC terminal is normally defined as the contention winner, and is bound by CICS, but CICS can accept a negotiated bind in which the contention winner is changed to the loser.
Session initiation can be performed in one of the following ways: