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Lesson 2Oracle Net at a high level
Objective Describe relationship between Oracle Net, client PCs, and database system.

Relationship Oracle Net ClientPcs Database

Oracle Net is a complicated beast, and there are many ways to configure it. Let us assume, for the moment, that you have a database server and several client PCs all running on a network, and all configured to use TCP/IP. The following mouseover shows how Oracle Net fits into the picture when these client PCs connect to the database.
  1. Client software, whether written by Oracle or by you, interfaces to Oracle Net.
  2. The Oracle Net interface is the same regardless of the underlying network transport protocol being used.
  3. The Oracle Net TCP/IP Adapter takes care of transmitting Oracle Net requests over the network using TCP/IP. Other adapters exist as well. The SPX adapter, for example, is often used in Novell NetWare environments.
  4. The Oracle Net Listener runs on the database server. Its job is to monitor the network for incoming Oracle Net requests.
  5. The Oracle Net Listener passes incoming requests to the appropriate server process.
  6. The server process interacts directly with the Oracle database.
  7. The database server is the computer on which the database resides.
Client PCs access Oracle databases over the network using Oracle Net.

Oracle Net Key Components

The above diagram represents the most common configuration of Oracle Net, and it's the one we are going to use for this course.

Oracle Net Listener

A key component of Oracle Net is the Oracle Net Listener. This is a process (or service on NT) that runs on the database server, and that monitors the network for incoming database connection requests. In order to access a database instance, such as the COIN instance, from a remote system, you must first tell the listener that the instance exists. This is done by editing a file named listener.ora that sits on the database server.

Oracle Net Client

Oracle Net also runs on client PCs that need to access an Oracle database. Just as you need to tell the Oracle Net Listener on the server about the databases on that server, you need to tell the Oracle Net client software on a PC about the databases to which you want to connect. In order to access COIN from a client computer, you need to tell the client that a COIN database exists, and you also need to point the client to the server where the listener for the COIN database resides. This is done by editing a file named tnsnames.ora that sits on the client PC.

Oracle Net Basic Concepts

Click the Exercise link below to complete a short matching exercise.
Oracle Net Basic Concepts