Order of deactivation

VTAM® deactivates resources in the opposite order from activation. When VTAM receives a command to deactivate a resource, it first deactivates any resources subordinate to the named resource, moving from the bottom of the hierarchy upward, and then deactivates the named resource. Deactivating resources can be disruptive to existing LU-LU sessions. However, depending on the type of connection, a resource can be deactivated without disrupting the LU session if you use TYPE=GIVEBACK on the VARY INACT or the VARY REL command.

Deactivation of certain VTAM resources requires more attention than does their activation. Be aware of the changing connectivity of the domain and the effects on the rest of the network of NCP major node and channel-attachment major node deactivation. Also consider the effects of cross-subarea link and link station deactivations on the operation of the rest of the network. In particular, you should be aware of the impact of deactivating any of the following resources:

An NCP through which other NCPs are attached to the network
A link or link station, whether channel or SDLC, that provides the only connection between a subarea and the rest of the network

VTAM deactivates a cross-subarea link to a host processor when the channel-attachment major node is deactivated. Deactivating this link (a channel) destroys any sessions using a route on that link, possibly including the SSCP session with another subarea node. Also, VTAM might be an intermediate routing node for cross-domain sessions that traverse the link. For this reason, care should be taken not to deactivate a cross-subarea link that could be supporting session traffic.

Note: When deactivating any channel-attachment major node, or any of its subordinate links or link stations, you might be deactivating a link that carries intermediate routing node traffic. Deactivating the link will disrupt these sessions.

When you enter a VARY INACT command for an NCP, VTAM does not deactivate any cross-domain link or link station unless CDLINK=INACT is specified on the VARY INACT command.

You can deactivate and reactivate CDRMs without disrupting active sessions. Use the SAVESESS operand on the VARY INACT command to specify whether active sessions should be terminated when you deactivate the CDRM. This operand enables you to keep active sessions when you use the FORCE or IMMED option of the VARY INACT command. However, SAVESESS specifies that all pending or queued sessions using the specified CDRM are terminated.

The loss of an SSCP-SSCP session (for example, as the result of a link failure) is not the same as external cross-domain resource manager deactivation and does not terminate existing LU-LU sessions. However, new sessions with logical units controlled by the SSCP that were lost cannot be started until the SSCP-SSCP session is reestablished.