Hi,

Please check the following.

1. PING : Check if PING works fine from DOS prompt.
C:> PING ip_address
where ip_address is the IP address of the server
where the database resides.

If it fails, Contact System Administrator to resolve the
problem.

2. If PING works fine, then try TNSPING.
C:> TNSPING dbname 3
where dbname refers to 4-letter database name and
3 refers to number of times it will try.

If it fails, Check the IP Address specified in TNSNAMES.ORA


If both work fine, then you should not be getting any problem.

Thanks.

Sundar