Defining independent LUs

You can define independent LUs in the following ways:

You can have your independent LUs defined dynamically by VTAM® during session establishment. See Dynamic definition of independent LUs.
You can define CDRSC definition statements (or model CDRSC definition statements) to represent your independent LUs. See Using CDRSC definition statements for independent LUs.
You can use standard LU definition statements with LOCADDR=0 coded. These LU definitions are converted into CDRSC definitions by VTAM when the major node is activated. This method is not recommended other than as a migration tool. Using this method, you cannot warm-start VTAM and have your independent LUs return to a before-failure condition. Independent LUs that are defined this way are converted to CDRSCs by VTAM and placed in the ISTPDILU major node. If a new resource is detected that matches an existing CDRSC, the new resource definition is integrated with the existing definition, and the resulting resource resides in the ISTPDILU major node. See Automatic conversion of independent LU definition statements.

For information about how VTAM handles multiple definitions of one independent LU resource, see the z/OS Communications Server: SNA Resource Definition Reference.

Migration: It is recommended that you remove predefined independent LU definitions from your device-type major nodes and either let VTAM dynamically define CDRSC definitions for the independent LUs on a session-request basis or create CDRSC major nodes. If you decide to code CDRSC major nodes for your independent LUs and you previously had them defined to the NCP, you should regenerate your NCP to avoid any address mismatch problems.

One of the advantages of removing existing LU definition statements for independent LUs (and using either dynamic definition of independent LUs or coding CDRSC definition statements) is that predefined, NCP generated addresses are not used by the independent LU. Addresses are requested as needed and are returned when no longer needed.

You can use multiple connections and the dynamic selection of session connections without dynamically defining your independent LUs as CDRSCs.

Note: If you have session takeover operations that rely on VTAM creating substitute LUs, these takeover operations can fail.