Ora-12545 Cannot connect to the host

Hi,
I am just curious anyone encounter the problem with Oracle 9iAS when connect to the oracle database. ORA-12545 Connect Failed because target host or object does not exist.

I am able to use tnsping to the hostname and IP address but why I couldn't run sqlplus ? What could be the problem ?

To clarify, my database and IAS sitting at the HP-UX 11.0

Database version = 8.1.7.0.0
IAS = 1.0.2

Thanks you.

This could be a problem with dns or host names file. Check and see if you can use an IP Address in your configuration files.

I understand that tnsping works, but its oracle and each tool behaves differently in the same environment.

dba