Selective termination of idle LU 6.2 sessions

You can limit the use of some network connections, such as lines. Defining a limited network connection enables you to limit the use of the connection and keep only active sessions on that connection. Sessions that are not active are terminated. If all sessions are terminated, then the connection is terminated. The best network connections to define as limited are lines and PUs whose cost is determined by the length of time a connection exists. Defining these as limited can help reduce switched line connect charges.

When a session traverses a limited connection, the session can be terminated if no conversation is detected for a set period of time. You must specify the timeout on the LIMQSINT operand of the APPL definition statement. LIMQSINT specifies how long (in seconds) unused limited resource sessions will remain on the queue before they are terminated.

Note: Only LU 6.2 conversations are affected by limited resource definition. Non-LU 6.2 sessions are unaffected and cannot be limited.

To use LU 6.2 limited resource management:

Determine which network connections you want to define as limited.
Define the network connections to VTAM® by coding LIMRES=YES on the GROUP, LINE, or PU statement. LIMRES is valid for PU types 1, 2, and 2.1 only.
Determine the time interval for VTAM to search the queue and define the interval to VTAM using the LIMQSINT operand on the APPL definition statement.

You can specify a line, a group of lines, or a PU as a limited resource for the following major nodes:

External communication adapter
Local SNA (PU only)
MODEL (PU only)
NCP
Switched (PU only)

After you define the resource to be limited, set the time interval for the queue search. As a starting point, you should specify a time interval at least 1 second less than half of the shortest line time cost interval. For example, if the line time cost interval is 120 seconds, you should specify 59 seconds on the LIMQSINT operand. You might need to adjust the time interval for different applications.

If you are using VTAM CMIP services, be aware that the selective termination of idle LU 6.2 sessions can affect CMIP services associations. An association is a cooperative relationship between application entities for data exchange. In this case, an application entity can be another CMIP services or CMIP application program.

VTAM CMIP services ends idle associations when either of the following conditions occurs:

Selective termination of idle LU 6.2 sessions is in effect and the timeout value has expired.
Selective termination is not in effect and VTAM CMIP services automatically ends the association because it is idle.

In either case, all idle associations are ended. Associations that were specifically requested by an application program (associations for which an application program issued an ACF.Associate request) are not affected by selective termination at the system where the ACF.Associate request was initiated, but can be terminated automatically on the system that was the target of the association.