Oracle Database Discussions

Hi,
I am using Oracle Database 10g on Enterprise Redhat Linux 5
I use a database link to connect to another Oracle database server.

I want to detect when database link is down to inform user
I use the simple statement
Select * from dual@db_server;
but it takes very long time to raise exception telling that connection is failed

Is there a way to decrease the timeout period in order to detect connection failure earlier ?

Thanks