Resolving logon mode names to subarea and APPN Classes of Service

VTAM® uses the logon mode table for the secondary LU (SLU) to initially resolve the logon mode name to a subarea COS. This happens at the VTAM that owns the SLU or at the Interchange Nodes (ICN) that must send a session request into the APPN network.

For sessions that will use APPN links, one of two methods is used to determine the APPN COS for the session. If a subarea-to-APPN (SATOAPPN) Class of Service mapping table has been defined at the VTAM that must choose the APPN Class of Service, it will be used to map the resolved subarea COS to an appropriate APPN COS. If a SATOAPPN Class of Service mapping table has not been defined, or a table is found with no matching entry, VTAM uses the logon mode table for the SLU (as defined in that VTAM node) to resolve the logon mode name to an appropriate APPN COS.

The same is true for session requests (or replies) received by VTAM from an APPN network that will also use subarea virtual routes. One of two methods is used to determine the appropriate subarea COS for the session. If an APPN-to-subarea (APPNTOSA) Class of Service mapping table is defined at the VTAM that must choose the subarea COS, it will be used to map the APPN COS received on the APPN session request (or reply) to an appropriate subarea COS. If an APPNTOSA Class of Service mapping table is not defined, or a table is found with no matching entry, VTAM uses the logon mode table for the SLU (as defined in that VTAM node) to resolve the logon mode name to an appropriate subarea COS.

Note: VTAM always uses the logon mode table for the secondary LU (SLU) to resolve the logon mode name to an APPN or subarea Class of Service, when needed. But at interchange nodes and for other node roles, the SLU might be a dynamic CDRSC. In this case, the IBM-supplied default logon mode table (ISTINCLM) would normally be used. If you want to have a different table used for these resources, you can use the DYNMODTB start option to specify a different logon mode table to be used for all dynamically created CDRSCs.