When a client issues a connection request using SCAN, the three SCAN addresses are returned to the client.

If the first address fails, then the connection request to the SCAN fails over to the next address. Using multiple addresses allows a client to connect to an instance of the database even if the initial instance has failed.

Oracle RAC provides failover with the node VIP addresses by configuring multiple listeners on multiple nodes to manage client connection requests for the same database service. If a node fails, then the service connecting to the VIP is relocated transparently to a surviving node, enabling fast notification of the failure to the clients connecting through the VIP. If the application and client are configured with transparent application failover options, then the client is reconnected to the surviving node.