OpenEdge allows client and server operation among Windows systems that communicate using TCP/IP. In an OpenEdge AppServer configuration, the client connection to the application server is always TCP. The OpenEdge AppServer supports all of the client/server network types for the connection of the application server to the database server.
The following figure shows the simplest OpenEdge network configuration—a database server machine and an application workstation. Although the figure shows only one database server machine and workstation, there can be more than one of each.
Figure 15. Simple OpenEdge network configuration
This configuration is typical of TCP/IP networks without file servers. There are no shared resources except the OpenEdge database. The application workstation and database server machine each have a hard disk. A printer is also attached to the application workstation. OpenEdge is installed on each node.
A workstation in this configuration often supports multiple users and clients (for example, a system with multiple terminals) who share the local printer and OpenEdge application. The database server machine is usually a high-performance back-end processor that can also support local self-service clients. This network configuration, with the OpenEdge database local to the database server machine, ensures full database integrity. With all files stored local to each node, it generally (but not always) provides the highest performance on a LAN.
The following figure shows a dedicated network file server, dedicated OpenEdge database server machine, and application workstations. Although the figure shows a limited number of workstations, file servers, and database server machines, there can be more of each.
Figure 16. Network file server for application files
This is a configuration typical of PC LANs with file servers and network operating systems. A hard disk and a printer are attached to the network file server, and an additional hard disk is attached to the OpenEdge database server machine. The OpenEdge database is on the disk drive that is locally attached to the OpenEdge database server machine. OpenEdge and all application procedures are installed on the file server and shared by all other nodes.
This network configuration ensures full database integrity and high performance, limited only by network and application performance capabilities.
The following figure shows a network file server doubling as an OpenEdge database server machine and disk-optional application workstations. Although the figure shows a limited number of workstations, file servers, and database server machines, there can be more of each.
Figure 17. Network file server as a database server
This is a configuration you might find on a PC LAN with a powerful file server running a multi-tasking operating system. OpenEdge, application procedures, and the OpenEdge database are all installed on the file server and are shared by the other nodes.
This network configuration provides full database integrity and acceptable performance on a file server with high-speed CPU and I/O resources.
Note: Avoid doubling a network file server as a database server machine on low-capacity nodes or on nodes where the database server machine can run only in an emulated environment.
The following figure shows database files residing on a network file server.
Figure 18. Network file server for application and database files
This network configuration runs the risk of compromising database integrity if the network file server or database server machine crashes, because the before-image (BI) file is on the network file server, making synchronous writes to it impossible. Performance also depends on whether network file server I/O efficiency compensates for traffic across the network.
An application server running on the application server machine connects through shared memory to an OpenEdge database and has access to a set of procedure files. An ABL application runs on the application workstation, connects to the application server running on the OpenEdge AppServer machine, and sends the requests to the application server to run remote procedures. The procedure execution and database access occur in a remote OpenEdge session context.
The following figure shows the simplest LAN configuration for OpenEdge on a network.
Figure 19. LAN configuration with the OpenEdge AppServer
In more complex implementations of the OpenEdge AppServer, an application server can connect to another application server in order to connect with a database. For more information about the OpenEdge AppServer, see OpenEdge Getting Started: Application and Integration Services.
