Sqlplus doubt


Oracle 9:
When i type sqlplus in command line and enter username and password, i can able to login in.

When i type sqlplus username@instance , it ask for password , when i type password it throws error .

Error: ORA-12154 ``TNS:could not resolve service name"

Please help me understand why it occurs , i googled but dont understand what they trying to convey.

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Wasim Akram ShaikCommented:
one of the probable reasons is your ORACLE_SID is set in your machine.. so you are connecting its directly taking the SID .. when you specify it via username/password@instance..

the @instance entry should be present in your tnsnames.ora file which is generally present in your <ORACLE_HOME>/Network/Admin Folder..
check out the entry which is present there.. if not make an entry here .. this should resolve your issue..
HuaMin ChenSystem AnalystCommented:
Try to see if you are able to ping the IP of Oracle database server machine.
Geert GOracle dbaCommented:
assuming windows here ...

you might have script on your computer like this


toad %1 %2 %3 %4 

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what happens if you type sqlplus without any parameters ?
can you see the header of sqlplus ?

and then enter user@alias
and password

and then what happens ?
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