Specifying values for session limit negotiation

The application program is responsible for specifying values used during session limit negotiation. VTAM® finds values for CNOS negotiation as follows:

If the application program sets negotiation values on the CNOS session limits control block using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction, VTAM uses those values.
If the application program does not specify a CNOS session limits control block, VTAM builds one. VTAM uses the defined negotiation limits from the LU-mode table to build the control block. These values would have to have been set previously by specifying a DEFINE control block using the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction. (You also can issue the MODIFY DEFINE command to set defined negotiation limits.)
If defined negotiation limits were not specified with an APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction, VTAM uses the values of the parameters coded on the APPL definition statement.
If parameters were not coded on the APPL definition statement, VTAM uses the defaults for the parameters: (2,1,1). The defaults are explained in the z/OS Communications Server: SNA Resource Definition Reference.

The values that can be negotiated during session limit negotiation are shown in Table 1.

Table 1. Values and parameters used in session limit negotiation
Value	Source	Set by	Stored
Defined negotiation limits	DEFINE control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction	LU-mode table
	APPL definition statement	Systems programmer	LU-mode table
	VTAM default values (2,1,1)	VTAM	LU-mode table
CNOS negotiation limits	CNOS control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction	LU-mode table
CNOS negotiation limits	CNOS control block	VTAM using defined negotiation limits from the DEFINE control block or the APPL definition statement	LU-mode table
Local draining responsibility	CNOS control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction	CNOS control block
Remote draining responsibility	CNOS control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction (Remote side might negotiate to not allow draining)	CNOS control block
Local draining acceptance	DEFINE control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction	LU-mode table
	APPL definition statement	System programmer	LU-mode table
	VTAM default value (DDRAINL=NALLOW)	VTAM	LU-mode table
Session deactivation responsibility	CNOS control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction	CNOS control block
Local session deactivation acceptance	DEFINE control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction	LU-mode table
	APPL definition statement	System programmer	LU-mode table
	VTAM default value (DRESPL=NALLOW)	VTAM	LU-mode table
Local security acceptance level	DEFINE control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=DEFINE macroinstruction	LU-mode table
	CNOS control block	Application program using the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction	LU-mode table
	APPL definition statement	System programmer	LU-mode table
	VTAM default value (SECACPT=NONE)	VTAM	LU-mode table