You can use the disconnect facility to specify whether VTAM® will automatically terminate the SSCP-PU and SSCP-LU sessions when the last LU-LU session is terminated. This is most applicable when the connection is only temporary. VTAM also will terminate the SSCP-PU and SSCP-LU sessions if no LU-LU session is ever established within a given period of time.

You can also specify a period of time, beginning when the last LU-LU session is terminated, during which VTAM delays termination of the SSCP-PU and SSCP-LU sessions. Delayed disconnection is beneficial if there is usually a minimal time period between the ending of LU-LU sessions and the start of new LU-LU sessions under the same PU.

For a physical unit on a switched link, disconnection means that the dial connection is broken, and the SSCP-PU session is terminated. Therefore, the telephone is hung up, thus potentially saving unnecessary telephone charges. However, the PUs and LUs are not deactivated. They remain in connectable status awaiting another dial-in or dial-out operation, or for a channel-attached resource, awaiting the device to be powered-on. Sessions can be requested with the logical units, and the request causes the physical connection to be reestablished.

You can enable the disconnect facility by coding the DISCNT operand on the PU definition statement.

If you code DISCNT=YES for a peripheral node, all of the SSCP-LU sessions and the SSCP-PU session for that physical unit are terminated after all LU-LU sessions are terminated. If any of the logical units (or the physical unit) requests its own session termination, VTAM ignores the HOLD part of a character-coded logoff or the LAST-NOTLAST part of a field-formatted Terminate Self request. VTAM also rejects any attempt made by the physical unit to terminate its own SSCP session with a discontact request. If HOLD=YES is specified or defaulted on a LOGOFF request, DISCNT=YES is ignored.

If you specify DISCNT=DELAY for a peripheral node, all of the SSCP-LU sessions and the SSCP-PU session for that physical unit are terminated after all LU-LU sessions are terminated and after the delay period expires. In addition, you can specify a period of time VTAM delays termination of the SSCP-PU and SSCP-LU sessions if no LU-LU session is ever established. The delay period is determined using the DISCNTIM start option (default is 15 seconds), unless this global limit is overridden by a delay period specified for a particular PU on the DISCNT=DELAY operand or using the MODIFY RESOURCE command.

The type of processing VTAM performs depends not only on the type of connection but also on whether the type of node attached is peripheral or subarea. For more information about switched connections between subarea nodes, see Implementing a subarea network.

The disconnect facility also enables you to specify whether the "final-use" status is to be sent for the deactivation request of the physical unit. VTAM sends the "final-use" status in the deactivate physical unit request if DISCNT=YES,F is specified. If you code NF, "not-final-use" status is indicated. This "final-use" status does not apply when DISCNT=NO, nor does it have any effect on the VARY INACT command.