Database Relays One of the problems in making middleware fit on existing networks is matching protocols between a more varied set of machines than ever before. While the average LAN consists of all Intel machines united by NetWare, the advent of RDBMSs often brings UNIX and even mainframe hosts into the picture. What network protocol should the NetWare client have in common with those hosts? Many network managers have no interest in supporting TCP/IP and even less interest in IBM SNA LU 6.2 protocols on every desktop. Nor is it often possible to run NetWare IPX/SPX or AppleTalk protocols on those host environments. The strict requirement for a single network protocol between clien t and server was a stumbling block for client/server implementatations. While basic database networking middleware implemented in an organization may support only a single common network protocol to connect the client and the server, a database relay device can link those clients to other hosts. Database relays are typically intermediate devices that accept connections from clients using one network protocol and connect to a remote host using a different protocol. Take a look at our diagram: [Diagram: Database Relay Components] The database relay differs from the database gateway [link] in that it only supports connections to the same RDBMSs as a direct protocol connection would have. It does not translate SQL dialects or data formats. For this reason, it is typically able to perform better than a full gateway, though still not as quickly as a direct connection between the server and client. As with routed networks (eg: any TCP/IP or NetWare IPX internetwork), any hop between client and server will have some impact. Microsoft offers a database relay service called SQL Bridge, but since NT already supports most protocols for most clients, it's not as needed as in the old days. For other middleware products on operating system platforms that don't offer the variety of network protocols that Windows NT does, this database relay function can become strategic. Oracle's Multi-Protocol Interchange (MPI) [link] is an example of a useful implementation of the relay approach. November 15, 1995 Print This Page E-mail this URL