A list of alternate database servers that is used to failover new or lost connections, depending on the failover method selected. See the FailoverMode property for information about choosing a failover method.
The server name (servername1, servername2, and so on) is required for each alternate server entry. Port number (port1, port2, and so on) and connection properties (property=value) are optional for each alternate server entry. If the port is unspecified, the port number of the primary server is used. If the port number of the primary server is unspecified, the default port number of 1521 is used.
Example
The following URL contains alternate server entries for server2 and server3.