Load Balancing and Oracle Net Services

Many applications like to balance their workloads across all the instances of an Oracle RAC database. Usually, load balancing with Oracle (excluding the parallel feature) meant connection load balancing—that is, the connections to the database are balanced on a “round-robin” basis, CPU load, or session count at connect time. With Oracle Net Services, there are two types of connection load balancing: one on the client side and the other on the server side.

NOTE

The discussion about connect-time load balancing is for dedicated connections only. Shared server connections can also take advantage of these features but are not discussed here.

Client-Side Load Balancing

Oracle’s client-side load balancing feature enables clients to randomize connection requests among all the available listeners. Oracle Net Services progresses through the list of protocol addresses in a round-robin sequence, balancing the load on various listeners. This normally is referred to as client-side connect-time load balance. Without client-side load balancing, Oracle Net Services progresses through the list of protocol addresses sequentially until one succeeds. Figure 13-1 illustrates client-side load balancing.