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Lesson 2 Oracle server components for Oracle Net
Objective Identify the main server components of Oracle Net.

Oracle Server Components for Oracle Net

An Oracle database server requires listener processes[1] to poll for incoming connections. These incoming connections can be from many protocols, and they can be TCP/IP connections, SPX connections, or even SNMP connections from a mainframe computer.
By the time the connection request enters the computer network, all the TNS work has already been done by the tnsnames.ora file, and the network packet contains all the information required to connect to the database. When an Oracle listener detects an incoming connection, the listener process bequeaths a server process and passes the connection information to this process. The server process, in turn, establishes the connection to the Oracle database.
To summarize, all that's needed for a server-side Oracle Oracle Net configuration is the listener daemon process (started with the Oracle command lsnrctl start), and the supporting listener.ora file.

Understanding Connectivity and Oracle Net Services

Oracle Net, a component of Oracle Net Services, enables a network session from a client application to an Oracle Database server. When a network session is established, Oracle Net acts as the data courier for both the client application and the database. It is responsible for establishing and maintaining the connection between the client application and database, as well as exchanging messages between them. Oracle Net is able to perform these jobs because it is located on each computer in the network.

About Client/Server Application Connections

Oracle Net enables connections from traditional client/server applications to Oracle Database servers. Figure 5-2 shows how Oracle Net enables a network connection between a client and a database server. Oracle Net is a software component that resides on both the client and the database server. Oracle Net is layered on top of network Oracle protocol support, rules that determine how applications access the network and how data is subdivided into packets for transmission across the network. In Figure 5-2, Oracle Net communicates with TCP/IP to enable computer-level connectivity and data transfer between the client and the database.
Figure 5 - 2: Client/Server Application Connection
Figure 5 - 2: Client/Server Application Connection

Oracle Net Components

Specifically, Oracle Net is comprised of the Oracle Net foundation layer, which establishes and maintains connections, and Oracle protocol support, which maps the foundation layer technology to industry-standard protocols.
  1. Oracle Net foundation layer: A networking communication layer that is responsible for establishing and maintaining the connection between the client application and server, as well as exchanging messages between them.
  2. Oracle protocol support: A software layer responsible for mapping Transparent Network Substrate (TNS) functionality to industry-standard protocols used in the client/server connection.
  3. Transparent Network Substrate (TNS): A foundation technology, built into the Oracle Net foundation layer that works with any standard network transport protocol.
[1] event listener:An event listener is a procedure or function in a computer program that waits for an event to occur