When the user connects to more than one database, there are two basic configurations:
Federated— All databases are local. The following figure illustrates federated database connections.
Figure 15. Federated database configuration
Distributed — One or more of the databases reside on one or more remote machines in the network, and OpenEdge sessions connect to the database using a single networking protocol. The following figure illustrates distributed database connections.
Figure 16. Distributed database configuration
A multi-tier configuration is more complex than the basic federated and distributed models. A multi-tier configuration consists of a database tier that supports self-service clients, an application tier that supports remote clients, and a thin-client tier. Multi-tier configurations might improve system performance for a large installation. The following figure illustrates a three-tier configuration.
Figure 17. Sample multi-tier configuration
The OpenEdge RDBMS architecture provides multiple simultaneous paths to a database. Each self-service client can access the database and service its own requests. Each network server queues and runs requests for one or more network clients. The database broker initializes shared memory and starts a new server for each additional client or set of clients that access the database. By removing the server as a bottleneck, the OpenEdge architecture increases overall performance.
Federated — All databases are local. The following figure illustrates federated database connections.
