Question on local listener in 11g R2 RAC

 

Hi,

In our 2 node 11g R2 RAC database, one of the DBA's have configured an additional listener LISTENER_APP in addition to the default listener LISTENER

Now our question is that

1. What could possibility be the benefit of adding a new LISTENER  (LISTENER_APP) in addition to the DEFAULT listener (LISTENER)

2. When the clients connects to the database via SCAN entry (we are using DNS and not GNS), the request will be routed to    one of the SCAN listeners (we have 3) and it will then route it to the LOCAL LISTENER on the least loaded node. So how do we know if the scan listeners will be routing the client request to the LISTENER or LISTENER_APP?