(1) In Managed System Services, a set of database files that contain topology information and general system information for nodes throughout the network.
(2) The representation of the current topology of the intermediate routing portion of the APPN network. The network topology database contains entries for network nodes and the transmission groups interconnecting them. Each entry describes the current characteristics of the node or transmission group that it represents. The topology database is used to determine the preferred session route between two end nodes for a given class of service.