Oracle RAC Load Balancing

The RAC load balancer is based on both client-side and server-based types:

Client

Configuration is relatively simple, add Load_balance=on in Tnsnames.ora, as follows:

RAC =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP) (HOST = RAC1-VIP) (PORT = 1521))
(ADDRESS = (PROTOCOL = TCP) (HOST = RAC2-VIP) (PORT = 1521))
(load_balance =on)
(FAILOVER = ON)
(Connect_data =
(SERVER = dedicated)
(service_name = RAC)
)
)

When the client connects to the RAC, it randomly picks a node to connect, because the client does not know the state of the node, the node hangs, there may be a long time TCP wait. After the 10g version, this situation has a great improvement, but the client does not know the number of the RAC node load and connections, there may be a node heavy burden, so that the balance can not play well.

Service side

After 10g, the server load balancer can balance each node according to the load and connection number of each node, and the Pmon process of each node will report its load situation to RAC on a regular basis.

The configuration is as follows:

Listeners_rac =
(Address_list =
(ADDRESS = (PROTOCOL = TCP) (HOST = RAC1-VIP) (PORT = 1521))
(ADDRESS = (PROTOCOL = TCP) (HOST = RAC2-VIP) (PORT = 1521))
)

ALTER SYSTEM SET remote_listener = Listeners_rac;

Sometimes the reporting load process delay leads to the balance effect is not obvious, when joined Prefer_least_loaded_node=off, the server will be allocated according to the number of connections.

Starting with Oracle 10.2, Oracle introduced the load Balance Advisor, which further improved load balancing. With service, you can set different load balancing policies for different service sets.

Oracle RAC Load Balancing