|Net8 Administrator's Guide
This chapter introduces Net8, and provides an overview of its main applications, features, and functionality. It contains the following sections:
Net8 is the foundation of Oracle's family of networking products, allowing services and their applications to reside on different computers and communicate as peer applications. The main function of Net8 is to establish network sessions and transfer data between a client machine and a server or between two servers. Net8 is located on each machine in the network. Once a network session is established, Net8 acts as a data courier for the client and the server.
Figure 1-1 shows a client-to-server connection:
Network sessions are established with the help of a listener. The listener is a separate process that resides on the server whose responsibility is to listen for incoming client connection requests and manage the traffic to the server.
The listener brokers the client request, handing off the request to the server. Every time a client (or server acting as a client) requests a network session with a server, a listener receives the actual request. If the client's information matches the listener's information, the listener grants a connection to the server.
For environments where a large number of connections need to access the same service, Net8 offers a routing process called Oracle Connection Manager that resides on a machine separate from the client or server. For further information about Oracle Connection Manager, see "Connection Routing Capabilities".
Net8 allows connections to various services, such Oracle databases, non-Oracle databases, gateways and external procedures (functions that can be called from PL/SQL code). As Oracle databases are the most common service, this section will focus on database services.
When an end user connects to a database service from across the network, a connect string identifies the service through a net service name. For example:
A net service name is able to access a service across the network by providing the network description information necessary to locate the service on the network. A net service name is resolved into the:
The listener, through a protocol, accepts the client connection. It verifies the client information with the information it has received from the database service, as well as information it has stored in its own configuration file, LISTENER.ORA. If the information matches, a connection is granted.
Configuration is accomplished by creating a list of the net service names that map to services and addresses of listener destinations and configuring a naming method by which to resolve the net service name. A naming method is a method by which a net service name is resolved.
Net8 supports the several categories of naming methods. Wherever you choose to store your service names, Net8 offers tools to easily configure net service names.
Net service names may be stored via an existing IP address translation mechanism.
Net service names can be stored in a local configured file called TNSNAMES.ORA on each client and server in the network. Because the TNSNAMES.ORA can be configured on individual clients, it allows you to fine tune for a particular client's needs.
If a third-party naming service is already configured in your environment, Net8 supports storing net service name information in it to avoid additional configuration.
Net service names and service addresses can be stored in a central directory of service addresses. This central store, called Oracle Names, is an Oracle-specific name service that maintains a central store of service addresses. When client applications request connections to servers using a simple name, the Net8 client contacts Oracle Names to resolve the service into a network address descriptor.
Figure 1-2 shows:
For more information about choosing the place to store net service names, see "Resolving Net Service Names".
Net8 offers connection routing for environments where:
Typical Net8 connections require the client and server to have the same protocol installed.
Connection routing is supported by Oracle Connection Manager, through which client connection requests are routed to the server.
Figure 1-3 shows how client connection are routed to Oracle Connection Manager, which resides on a separate machine in the network:
See "Oracle Connection Manager Architecture", for further information.