CNM routing table

VTAM® uses a communication network management (CNM) routing table to determine which CNM application program is to receive an unsolicited network-services request unit that requires further processing. An application program can embed its own procedure-related identifier (PRID) in each request sent to VTAM. When a reply to the request is returned, VTAM uses the PRID to route the reply to the application program. Unsolicited RUs contain network information but do not contain a PRID. VTAM uses the CNM routing table to determine which application program is to receive the unsolicited RU.

IBM® supplies default routing information for the following CNM application programs:

The NetView® program
Alias name translation facility (supplied by IBM as part of the NetView program)
Downstream load utility

The IBM-supplied CNM routing table is named ISTMGC01. See IBM-supplied CNM routing table for a listing of the IBM-supplied CNM routing table.

For any application other than the default CNMTABLE to route unsolicited RUs to the application program, modify the default and give it a new name. You can name your supplemental table any 1- through 8-character name, but do not use ISTMGC00 as a table name if you are using multiple CNM routing tables because VTAM will always look for ISTMGC001 first and use that when VTAM is starting with a particular set of libraries. You might choose instead to select a 1- through 8-character name and specify the CNMTAB= start option. This allows you to have different CNM tables stored in the same set of VTAM libraries, which results in the following benefits:

You can start VTAM with different CNM tables.
You can run VTAM with different characteristics at different times.
You can run two VTAMs that are different at the same time.
You will have an old copy and a backup copy.

If you are starting multiple VTAMs that use the same VTAM library, you can have multiple supplemental CNM routing tables. Use the CNMTAB start option to associate a specific CNM routing table with the VTAM being started.

Whenever VTAM receives an unsolicited RU, VTAM uses the value specified on the CNMTAB start option to route the request.

If you do not specify the CNMTAB start option or specify CNMTAB=ISTMGC00, VTAM will use ISTMGC00, if available. No message is issued if ISTMGC00 is not found. In this case, VTAM uses the IBM-supplied table, ISTMGC01.
If you specify a name other than ISTMGC00 on the CNMTAB start option and it is not found by VTAM, message IST116I is issued.

Any user-supplied table used by VTAM overrides the IBM supplied table, ISTMGC01.