Oracle Net Services provides the ability to distribute client connections across the instances in an Oracle RAC configuration. There are two types of load balancing that you can implement: client-side and server-side load balancing. Client-side load balancing distributes the connection requests across the listeners, independently at each client. With server-side load balancing, the SCAN listener directs a connection request to the best instance currently providing the service, based on the -clbgoal and -rlbgoal settings for the service.
In an Oracle RAC database, client connections should use both types of connection load balancing.
See Also:
Oracle Database Net Services Administrator's Guide for detailed information about both types of load balancing