Application programs that use nonparallel sessions require only one address to represent the primary LU to all of the secondary LUs. However, application programs that use parallel sessions require a unique address to represent the primary LU to each one of the secondary LUs. If you plan to have cross-network parallel sessions, the network containing the secondary LU must have one element address for each parallel session with the primary LU. In the network of the primary LU, only one element address is required for all sessions with the secondary LU. Therefore, the number of addresses you should reserve in any particular network to represent application programs in other networks depends on whether the application program requires a unique primary LU address for each of its sessions.

For example, if terminals in your network are logged on to an application program such as CICS®, you need only one element address in the gateway NCP to represent that CICS to your network. If parallel sessions are established between your CICS system and the CICS in the other network, the PLU must use an address for each session. If your CICS is acting as the SLU for these parallel sessions, an element address is required for each session in the gateway NCP to represent the PLU to your network. If the CICS in the other network is acting as the SLU for these parallel sessions, only one element address is required in the gateway NCP to represent that CICS as the SLU to your network.

The gateway NCP needs an additional address for the other network to represent each of your CICS parallel sessions to the other network. The gateway NCP also needs element addresses to represent your terminals to the network containing the other CICS.