APPNCOS start option
Specifies the APPN Class of Service to be used if a requested Class of Service cannot be found in the topology and routing services Class of Service database. See IBM-supplied APPN Classes of Service for the names of the seven classes of service and APPN Class of Service definitions for information on implementing a user-defined Class of Service.
If a requested Class of Service cannot be found, the value you specify in APPNCOS is substituted for it, and there is a possibility that the characteristics of the substitute Class of Service are not the ones you intended for the route.
For example, a secure Class of Service might have been intended, but the substitution provided in APPNCOS might offer a Class of Service that uses unsecured links.
You can change the value of APPNCOS with the MODIFY VTAMOPTS command while VTAM® is running.