Introducing Oracle Network Products

This chapter covers the following topics:

Oracle Connectivity Overview

Architectural Overview

Client/Server Interaction

Oracle Connectivity Overview

Oracle Network Products' main function is to establish sessions and transfer data between a client and a server or between two servers. Most of the activity occurs at the beginning when setting up the session. Once the session is established, Oracle Network Products' main job is to act as a data courier for the client and server. The connection operation is initiated during any standard database login between the client application and the server, with information such as the client machine name and username being passed to the remote machine. Oracle Network Products coordinate a session with the help of a listener. Every time a client (or server acting as a client) requests a session with a server, the actual requests comes into a listener. The listener decides where the server is and enables the client to connect to the server. The listener is a separate process whose whole responsibility is to listen for incoming client connection requests and manage the traffic to the server.

Architectural Overview

Forming the foundation of Oracle Network Products is SQL*Net. SQL*Net uses the Transparent Network Substrate (TNS) and industry-standard network protocols (such as TCP/IP) to connect a client to a server and establish an Oracle session. Figure 1-1 shows the basic connectivity architecture.

Figure 1-1 SQL*Net Connectivity Architecture

Following is an overview of the Oracle network connectivity components:

SQL*Net

SQL*Net is a software layer required to communicate between Oracle clients and server. The role of SQL*Net is to establish and maintain a connection between the client application and the server and exchange messages between them. It provides both client-server and server-server communications across any network. It enables client tools to access, modify, share, and store data on Oracle7 databases over a network. The communication between client applications and server takes place across one or more networks, and is referred to as client/server communication.

Transparent Network Substrate

The TNS is an underlying layer of SQL*Net that receives requests, and settles all generic connectivity functions such as opening/closing a session or sending/receiving requests or responses. TNS then passes control to an Oracle Protocol Adapter to make the protocol-specific call.

Oracle Protocol Adapters

The Oracle Protocol Adapters are responsible for mapping TNS functionality to industry-standard protocols used in the client/server connection. Each adapter is responsible for mapping the equivalent functions between TNS and a specific protocol. An Oracle Protocol Adapter translates (or adapts):

function calls of specific network protocols (such as TCP/IP) into equivalent function calls of TNS.

TNS generic function calls into specific function calls for the underlying network protocol.

Table 2-1, "Oracle Network Products Availability" in Chapter 2, "Supported Oracle Network Products" lists the Oracle Protocol Adapters supported.

Additional Information:

See the third-party network documentation that came with your protocol software for a detailed technical discussion of these protocols.

Network-Specific Protocol Stack

The network protocol stack, not provided by Oracle, supplies a reliable means of communication. All Oracle software in the client/server connection process requires an existing network protocol stack to make the machine-level connection between the two machines. The network protocol is responsible only for getting the data from the client machine to the server machine, at which point the data is passed to the server-side Oracle Protocol Adapter.

Client/Server Interaction

This section describes a basic client/server connection.

Client Connection Request

The user requests a database connection from the server by supplying input (SQL command) through a client side application such as SQL*Plus. The application sends the request to SQL*Net to be transported across the network to the server. After the connection request is accepted by the listener on the server, the client application requests database information from the server.

Server Response to Client Connection Request

The server runs the Oracle7 database software and a SQL*Net network listener program. The SQL*Net network listener, through an Oracle Protocol Adapter, accepts connections from client applications on the network.

SQL*Net on the server delivers the client data transfer request to the Oracle7 database. The database performs the function requested by the user on the client machine. Finally, SQL*Net transfers the results of the database functions to the client machine.

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