The application program issues the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction to set the defined negotiation limits specified in the DEFINE control block. Otherwise, VTAM® sets the default defined negotiation limits using values on the APPL definition statement. (The defined negotiation limits on the APPL definition statement are specified before a CNOS negotiation takes place.)

Defined negotiation limits can be predefined for use during CNOS negotiation when no other values are available. They are set for each logon mode and stored in the LU-mode table with the session limits. They are different from session limits.

When VTAM is the target of a CNOS request, VTAM uses the defined negotiation limits as the target application program's bid in the CNOS negotiation. These limits are not necessarily the final negotiated limits.

For example, an application program might have (10,5,5) as the defined negotiation limits for a logon mode, but when a CNOS negotiation completes with a partner LU, the resulting session limits might be negotiated to (4,2,2). VTAM enforces the (4,2,2) limits on that logon mode group.

The defined negotiation limits are also used when VTAM is the source side of the CNOS request and the application program does not specify a CNOS session limits control block.