The ADDRESS_LIST parameter allows multiple addresses to be specified for a single TNS service name. For a multi-threaded server, each ADDRESS is another listener for the same node.
For Oracle Parallel server, each ADDRESS is another database node.
The SOURCE_ROUTE is typically used to enable Oracle Connection Manager features. When set to YES or ON, it means that all the addresses listed must be connected by the Connection Manager before the client can do anything on the databases.
This might be useful for distributed systems where committing transactions might cross multiple databases.
When LOAD_BALANCE is set to ON, connection load balancing is in force. Connection load balancing will be examined in a later module.
When the FAILOVER parameter is ON, transparent application failove is in force. This allows Oracle8i to re-connect to another server if the current connection fails. This is discussed in a later module.