Oracle7 Server Distributed Systems Volume I: Distributed Data

**SQL*Net and Network Environment Independence**

Just as SQL*Net connects clients and servers that operate on different nodes on a network, it also connects database servers across networks to facilitate distributed transactions. For example, when an application requests data from a remote database, the local database server communicates with the remote database through the network, using network communications software and Oracle's SQL*Net.

SQL*Net's advantage is that it runs on most networks. The particular type of network protocol, brand, or topology does not matter. In fact, it is feasible for a distributed system implemented using SQL*Net to work over different types of communication networks simultaneously.

Media/Topology Independence

SQL*Net supports most third-party network software packages, which in turn, support a wide variety of network hardware devices. On some platforms, a single Oracle Protocol Adapter can operate on hundreds of different network interface cards. This compatibility allows you to deploy applications in virtually any network environment, including Ethernet, Token-Ring, FDDI (Fiber Distributed Data Interface), ATM (Asynchronous Transfer Mode), wireless, and others.

When a request for a connection is made successfully, SQL*Net passes control of the connection to the underlying protocol. At that point, all media and/or topologies supported by the underlying network protocol are indirectly inherited by SQL*Net. SQL*Net allows the network protocol to use any means of data transmission, such as Ethernet, Token Ring, FDDI, or SDLC, to accomplish the low-level data link transmission between the two computers.

In addition, because SQL*Net connects to the network infrastructure through standard, high-level protocols, it also works with network components at lower levels such as bridges, routers, gateways, and packet switches.

Protocol Independence

SQL*Net provides protocol independence to its applications. Any application built on any computer running any protocol can be distributed without change to other computers running other protocols. An application using SQL*Net can run over any network protocol. SQL*Net's architecture provides the industry's broadest support for network transport protocols, including TCP/IP (Transmission Control Protocol/Internet Protocol), Novell SPX/IPX (Sequenced Packet Exchange/Internet Packet Exchange), IBM LU6.2, DECnet, OSI, and others.

In addition to supporting different protocols, SQL*Net also supports many vendor's protocol stacks, eliminating the need to purchase and install additional protocol support hardware or software. Without changing your existing infrastructure, you can transparently connect any combination of PC, UNIX, legacy, and other systems, using the network software you already have.

Any connection that works reliably at the protocol level will work with, and be transparent to SQL*Net, regardless of the number of physical connections and transformations the packets go through between the two machines.

When connectivity is required between different high-level protocols, such as from SPX/IPX to TCP/IP, the Oracle MultiProtocol Interchange can provide automatic protocol conversion, a task that cannot be performed at lower levels in the network stack. This means that networks running different protocols can communicate with each other.