If you are using Oracle 10g, no LogicalHostname resources are required.
To ensure that Oracle listeners can continue to access the database after failure of an instance on a node, each node requires a logical hostname resource. On each node, the scalable Oracle listener listens on an IP address that is represented by the logical hostname resource.
If a cluster node that is running an instance of Oracle RAC fails, an operation that a client application attempted might be required to time out before the operation is attempted again on another instance. If the Transmission Control Protocol/Internet Protocol (TCP/IP) network timeout is high, the client application might require a significant length of time to detect the failure. Typically, client applications require between three and nine minutes to detect such failures.
In such situations, client applications can connect to listener resources that are listening on an address that is represented by the Sun Cluster logical hostname resource. If a node fails, the resource group that contains the logical hostname resource fails over to another surviving node on which Oracle RAC is running. The failover of the logical hostname resource enables new connections to be directed to the other instance of Oracle RAC.
Create one logical hostname resource for each listener that the listener resource represents.
Configure each logical hostname resource in a separate resource group.
Set the listener resource to depend on the logical hostname resources for all listeners that the listener resource represents.
Ensure that each node is the primary node of one resource group.
Ensure that the logical hostname resource is failed back to the primary node when the database instance on the primary node recovers after a failure.