Dear agasimani,

Before answering to this probelm i have some question to get the clear pic of the netowrk envoirment over there with you.
1) How are u accessing the db? From Oracle client software or Oracle developer i.e forms, reports?
2) What is the start in dir. of the SQL which is able to connect to the link? is it with the developer or the ora client part?
3)Show me the TNSNAMES entry on the board.

I hope if i get more details i could be able to help you..

Regards,
NK