Oracle connection extremely slow(Oracle 11G on Linux RHEL4)

Question

Hi guru,
In my production database connection suddenly starts taking significant time like 10-15 seconds.
even I try to connect from same machine by using following command :
sqlplus system/impetus@DB
it is taking more then 10 seconds every time
whereas if I use follwing command :
sqlplus system/impetus
connection is instant (taking only few milliseconds)
We also used tnsping which is also instant ...
any clue

Answer 1

The problem is of course the DNS entry (as indicated in one of the responses above) configured either at OS installation or later. Whatever the case, it is of primary improtance. On the other hand, one might have to prepare Oracle totally disconnected from the network (which is what I prefer, anyway). This is what I usually make sure off before proceeding and I also get a static IP from my administrator first (although not a must):
Example
eth0 interface (static):
IP : 192.168.1.101
SM : 255.255.255.0
GW: 192.168.1.101
DNS: 192.168.1.101
/etc/hosts :
127.0.0.1 localhost
192.168.1.101 myhost.acme.com myhost (replace myhost with your actual server hostname)
The above entires are a minimum for a succesful Oracle DB installation. Assuming you have completed the installation and have a created a database, you will find all connections working "normally" and the way it should.
Finally, (after I'm satisfied alls well), I get my network administrator to give me the correct entries for GW, DNS and make the necessary substitutions in the lan interface and /etc/hosts. Or have the administrator do it for you.
Hope this helps.