Dynamic definition of cross-domain resources

You do not have to define resources controlled by VTAMs in other domains. VTAM® can dynamically create the definition statements to represent resources that reside in other domains. The operands on the CDRM definition statement for the host CDRM and the external CDRM determine whether VTAM can dynamically create CDRSC definition statements.

Notes:

You can also dynamically define independent logical units within the same domain using this function, and independent logical units in nonnative networks. See Dynamic definition of independent LUs.
To define two or more cross-domain destination LUs that have the same name but are in different networks, use the NQNMODE=NQNAME start option. Otherwise, name conflicts cause session requests involving these LUs to fail.

To have resources in other domains dynamically defined to VTAM:

Code your host CDRM with CDRDYN=YES.
Code your external CDRM with CDRSC=OPT.

Now all unidentified resources residing under that external CDRM will be dynamically defined to your VTAM (host CDRM). Following is a sample coding for dynamic definition of resources in another domain:

         VBUILD TYPE=CDRM
MYHOST   CDRM  CDRDYN=YES,                                             X
               SUBAREA=1
HOST2    CDRM  CDRSC=OPT,                                              X
               SUBAREA=2

Dynamic definition can occur in the following two directions:

When VTAM receives a session request from an undefined cross-domain resource, the cross-domain resource is the originating logical unit for this session. For example, a terminal in another domain attempts to log on to an application in your domain. The external cross-domain resource manager initiates the session, sending a session request to your VTAM. If the terminal is not defined to your VTAM as a cross-domain resource, VTAM does not accept the session request unless the host CDRM definition is coded with CDRDYN=YES and the external CDRM is coded in your VTAM with CDRSC=OPT.
When VTAM sends a session request for an undefined cross-domain resource, the cross-domain resource is the destination logical unit for this session. For example, a local terminal attempts to log on to an application in another domain. If the application is not defined as a cross-domain resource, VTAM can still attempt to establish the session by sending a session request to adjacent SSCPs. VTAM sends the session request only if the host CDRM is coded with CDRDYN=YES and the adjacent CDRMs to which VTAM routes the session request are coded with CDRSC=OPT.

When VTAM creates dynamic CDRSCs for destination logical units, it must then dynamically locate the domain in which the resource resides. For this type of dynamic cross-domain resource, VTAM uses a search mechanism to route a cross-domain session request to other adjacent VTAMs. The mechanism is called an adjacent SSCP table and is described in Static definition of cross-domain resources.

Dynamically defined cross-domain resources are collected in a CDRSC major node named ISTCDRDY. ISTCDRDY is activated automatically during VTAM initialization, and deactivated automatically during VTAM termination.

The dynamic cross-domain resource definition occurs when you have defined the host to allow dynamic definition of CDRSCs.

In general, you have the same control of dynamically defined cross-domain resources as predefined cross-domain resources. You can display and deactivate dynamically defined cross-domain resources using operator commands.

You also generally have the same control of the CDRSC major node ISTCDRDY as other CDRSC major nodes. The DISPLAY ID, MODIFY CDRM, VARY ACT, and VARY INACT commands can all be used for the ISTCDRDY major node.

While the host CDRM is active, the operator can deactivate ISTCDRDY with the VARY INACT command, in which case all dynamically defined CDRSCs are also deactivated and the dynamic CDRSC definition function is disabled. The dynamic CDRSC definition function remains disabled until ISTCDRDY is activated again. You can activate ISTCDRDY again by issuing a VARY ACT command naming ISTCDRDY directly, or by activating the host CDRM (even if the host CDRM is already active). If the host CDRM is inactive, or if the host CDRM is not defined to allow the dynamic CDRSC definition function, activating ISTCDRDY does not provide the dynamic CDRSC definition function.

Dynamically defined CDRSCs are deactivated and deleted by VTAM on a periodic basis if they are not in use, based on the setting of the timer specified in the CDRSCTI start option. A dynamically defined CDRSC is also deleted if the host that owns that resource fails and the shadow resource for the CDRSC becomes the active definition. For more information about shadow resources, see Shadow resources.