Using the dynamic switched definition facility, you can dynamically create definitions for types 1, 2, or 2.1 switched dial-in devices, and for leased devices that appear to VTAM® to be switched (for example, devices connected by NTRI). You cannot dynamically define type 4 or type 5 devices. To create the dynamic definitions, this facility uses information provided by an installation-supplied exit routine and coded in a model major node.

The dynamic switched definition facility requires model definition statements and a configuration services XID exit routine. VTAM uses the model definitions to create the dynamic switched major node, from which definitions are taken to build dynamic switched devices.

A configuration services XID exit routine is invoked when an unknown device dials in to VTAM. The exit uses IDBLK, IDNUM and other parameters from the XID vector to gather resource definition information. The exit returns to VTAM the model statements, an optional dynamic switched major node name, and the names for the new PU and LUs.

If necessary, VTAM builds a dynamic switched major node. The new devices are added to the major node. If the exit does not specify a major node name, VTAM uses ISTDSWMN. Figure 1 illustrates the process of creating resources in a dynamically switched node.

Figure 1. Creating resources in dynamic switched major node

In Figure 1, when device PUA dials in to VTAM, PU and LU definitions from MODEL 11 are used by a configuration services exit routine to create resources in an existing dynamic switched major node, DYNMAJ1. When device PUZ dials in to VTAM, PU and LU definitions in MODEL 11 and MODEL 12 are used by the exit routine to create resources in dynamic switched major node, DYNMAJ2. Because dynamic switched major node DYNMAJ2 did not already exist, it, along with its resources, was created by this process.