Two LUs in different hosts can request a conversation at the same time, and the VTAM® in each host can choose the same session for both conversations. Such a situation is called contention. For a specific session, one of the partner LUs is the contention winner and the other partner LU is the contention loser. Contention winner versus contention loser is decided during BIND negotiation. The choice of contention winner versus contention loser is primarily due to information learned during the change number of sessions (CNOS) negotiation.
A contention loser can request use of the session from the contention winner. For VTAM-supported LU 6.2 application programs, VTAM requests use of sessions on the contention-loser side and grants or denies use on the contention-winner side.
LUs capable of parallel sessions can divide the contention-winner role between them for their sessions. For example, if two LUs have five parallel sessions, one LU might be designated the contention winner for three sessions and the other LU the contention winner for two sessions. The number of contention winners can be established at system definition time or dynamically. VTAM-supported LU 6.2 application programs are involved in setting the numbers of contention-winner and contention-loser sessions.