Why we need VIP in Oracle 10g RAC

In Oracle RAC database if user process is trying to get connection with some listener and found listener is down or node is down then Oracle RAC automatically transfer this request to another listener on another node. Up to Oracle 9i we use physical IP address in listener configuration. Means if requested connection gets failed then it will be diverting to another node using physical IP address of another surviving node. But during this automatically transfer, connection should need to wait up to get error message of node down or listener down using TCP/IP connection timeout. Means session should need to wait up to getting TCP/IP timeout error dictation. Once error message is received oracle RAC automatically divert this new connection request to another surviving node.Using physical IP address there is biggest gap to get TCP/IP timeout for failover suggestion. Session should need to wait for same timeout. High availability of Oracle RAC depends on this time wasting error message.

 

In Oracle 10g we have a concept of Virtual IP.Using virtual IP we can save our TCP/IP timeout problem because Oracle notification service maintains communication between each nodes and listeners. Once ONS found any listener down or node down, it will notify another nodes and listeners with same situation. While new connection is trying to establish connection to failure node or listener, virtual IP of failure node automatically divert to surviving node and session will be establishing in another surviving node. This process doesn't wait for TCP/IP timeout event. Due to this new connection gets faster session establishment to another surviving nodes.

Virtual IP (VIP) is for fast connection establishment in failover dictation. Still we can use physical IP address in Oracle 10g in listener if we have no worry for failover timing. We can change default TCP/IP timeout using operating system utilities or commands and kept smaller. But taking advantage of VIP (Virtual IP address) in Oracle 10g RAC database is advisable.

Using VIP configuration, client can be able to get connection fast even fail over of connection request to node. Because vip automatically assign to another surviving node faster and it can't wait for TNS timeout old fashion.