Defining switched resources used by multiple VTAMs

This section describes the coding methods that can be used when switched resources exist in a configuration that allows them to connect to a number of VTAMs in the network. There are two ways to define switched resources when the resource can be connected to multiple VTAMs.

Define switched resources through the switched major node in each host.
This method allows all VTAMs to activate the switched major node concurrently, causing the resource to be in CONCT state for each host. After a connection is made through a particular host, the resource is in ACTIVE state for that host.

A subsequent session request flowing through a host where the resource is in CONCT state causes a dial-out to the resource to fail. The host receiving the dial-out failure will reroute the request to another host. The request continues to be routed until the resource is located and the session is established through the host where the resource is in ACTIVE state. The session request is rejected if the resource is not located in the network.

Note: For dial-out connections to an LU in another network, network ID (NETID) must be specified on the PU definition statement.
Define switched resources through the switched major node and CDRSC definition statements.
Using this method, all hosts contain both switched major node and CDRSC definition statements for the resource.
- When the switched major node is activated, the associated PU and LUs are initially in a CONCT state.
- When the CDRSC definitions are activated, the associated LUs are changed into a shadow resource and the CDRSC definitions become the real resource. The CDRSC definitions for the LUs are then put in a CONCT state.
For additional information about shadow resources, see Shadow resources.
During the activation processing started by a dial-in request from a PU, the PU is put in an ACTIVE state. In addition, VTAM® changes the LU definitions to real and the CDRSC definitions to shadow. A result of this processing is that the owning VTAM recognizes the resource as real and all other VTAMs recognize the resource as a CDRSC.

Other VTAMs in the network receiving a subsequent session request for the PU and its LUs recognize the resources as cross-domain resources. The session request is rerouted until it reaches the VTAM which has the real LU definition as ACTIVE. (Only the VTAM owning the PUs has the LUs as ACTIVE.)

The disadvantage of this method is it requires a duplicate CDRSC to be defined for all LUs that might be the target of a search while the PU is connected to a VTAM.