Load Balancing and Failover with Oracle 10gR2 RAC

Oracle Net is a software component that resides on the client and on the Oracle database server. It establishes and maintains the connection between the client application and the server, and exchanges messages between them using industry standard protocols. For the client application and a database to communicate, the client application must specify location details for the database it wants to connect to, and the database must provide some sort of identification or address.On the database server, the Oracle Net Listener, commonly known as the Listener, is a process that listens for client connection requests. The configuration file for the Listener is the listener.ora.The client uses a connect descriptor to specify the database to which to connect. This connect descriptor contains a protocol and a database service name. When a client requests a connection, the Listener on the server receives the request and forwards the connection to the Oracle database. You can define your connect descriptors in the tnsnames.ora file on the client machine, or include them as part of the connection request.When the client connects to the cluster database using a service, you can use the Oracle Net connection load balancing feature to spread user connections across all of the instances that are supporting that service. There are two types of load balancing that you can implement: client-side and server-side load balancing.In an Oracle RAC database, client connections should use both types of connection load balancing. When you create an Oracle RAC database using Oracle Database Configuration Assistant (DBCA), DBCA configures and enables server-side load balancing by default.

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