# The problem
When you try to login to Oracle database through SQL*Plus, you get the error:
Error : ORA-12514 : TNS: Listener does not currently know of the service requested in connect descriptor.
Check the following:
- You setup correctly the listener.
- ORACLE_SID is the correct one.
- export ORACLE_SID=
Where is the name that you have given during database installation.
- sqlplus "/as sysdba"