Number and representation of sessions

If one LU in an LU-LU pair has only contention-loser sessions available, it might not be able to start a conversation because its partner gets first priority on using all sessions. To prevent this, the LU-LU pair negotiates a guaranteed number of contention-winner sessions for each LU, in addition to the overall session limits for the exchange.

The number of sessions, or session limit values, is negotiated between an LU-LU pair for each logon mode used. These values are described as follows:

Value: Description
SESSLIM: Overall session limit, which is the maximum number of concurrent sessions active between two LUs, using a given logon mode name
MINWINL: Number of contention-winner sessions guaranteed to the local LU, using a given logon mode name
MINWINR: Number of contention-winner sessions guaranteed to the partner LU, using a given logon mode name

In this publication, these values are shown as a triplet of numbers, (6,4,2), which represent the three types of session limits that are negotiated: SESSLIM, MINWINL, MINWINR. Use this type of notation when issuing a MODIFY CNOS command.

The same session limits are written differently for each partner LU. For example, if LU A and LU B negotiate the following session limits for a logon mode:

The overall session limit is 6.
LU A is guaranteed 4 contention-winner sessions.
LU B is guaranteed 2 contention-winner sessions.

The session limits for LU A on that logon mode would be written (6,4,2), and the same session limits for LU B would be written as (6,2,4); Figure 1 illustrates this.

Figure 1. Results of session limit negotiation

The sum of MINWINL and MINWINR cannot be greater than SESSLIM. However, the sum can be less than or equal to SESSLIM. Either partner LU can attempt to activate more than its guaranteed number of contention-winner sessions so long as the overall session limit is maintained.