LU mapping selection rules

LU mapping selection can become complicated because of the many variations of mapping statements, TN3270E versus TN3270 connections, Generic versus Specific connection requests, printer association, and LU mappings based on application name. LU mapping is very different between TN3270E and TN3270 and will be discussed separately. But first, some general Mapping Rules for both TN3270E and TN3270 follow:

• If multiple LUMAP statements exist for a Client Identifier all Specific LUMAPs are searched (TN3270E only) and then all Generic LUMAPs are searched in the order they are listed in the profile.
• If the application is known during the LU lookup and the ALLOWAPPL or RESTRICTAPPL-USER statement has LUs listed, then the found LU must be in both the mapped LU group and in the application LU group.
• When an LU match is found, the search stops.
• Telnet performs database lookup for Objects based on the Client Identifier. TN3270E connections require an Early Lookup so Telnet can give the client an LU name during connection negotiation. In all cases a Complete Lookup is done when the application name is known. Telnet performs an Early Lookup and a Complete Lookup for TN3270E connections. Telnet performs only a Complete Lookup for TN3270 and Linemode connections.