ORA-12154: TNS:could not resolve service name

[sambavan]

Have you set the

  export ORACLE_SID=O9IDB

in your environment. Then make sure that your listeners are up and functioning using

 lsnrctl status
  
 if down then:
  
    lsnrctl start

for connecting as follows

  sqlplus scott/[email protected]

Hope this is the problem

-Sam