Redhat Update question

[Khachatur Shahinyan]

Dear Redhat Users, I have two question about Redhat Linux updating 
procedure. First: Is it possible to update the server's major version, 
like from RHEL4 to RHEL5, online? And the second, what should i do to 
update my server if it is not connected to internet.
For additional information: I'm running RHEL AS4 on two machines, one is 
the "real" server and it is not online, and the second one is "testing" 
server which is online.
I'm  new  to  Redhat , and any help will be appreciated.

Thank You and Best Regards
Khachatur Shahinyan