Building a CNOS session limits control block

The CNOS session limits control block (ISTSLCNS) is used to:

Provide the CNOS session limits that VTAM® is to use to process a CNOS request from an application program.
Return the negotiated values—both to an application program that issues a CNOS request and to an application program that is the target of a CNOS request—provided the target application program has an ATTN exit.

Building a CNOS session limits control block is an optional action. If you request a CNOS session limits control block by issuing the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction, set the AREA field of the RPL to point to the control block and set the AREALEN field of the RPL to decimal 16, the length of the control block.

If you provide the CNOS session limits control block, when the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction completes, VTAM sets in the control block the updated values that were negotiated. For details on setting the address of the control block and its length in the RPL, refer to the z/OS Communications Server: SNA Programmer's LU 6.2 Reference.

Note: When a CNOS session limits control block is specified on the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction, initialize all fields in the control block, even when only one field is to be changed. If the application program does not specify a CNOS session limits control block, VTAM uses previously defined negotiation limits found in the LU-mode table. For more information on defined values, see How defined negotiation limits are set. Table 1 shows the values for each field.