ORA-12514 TNS:listener does not currently know of service requested in connect descriptor

I had this issue and the fix was to make sure in tnsnames.ora the SERVICE_NAME is a valid service name in your database. To find out valid service names, you can use the following query in oracle:

select value from v$parameter where name='service_names'

Once I updated tnsnames.ora to:

TEST =
   (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = *<validhost>*)(PORT = *<validport>*))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = *<servicenamefromDB>*)
    )
)

then I ran:

sqlplus user@TEST

Success! The listener is basically telling you that whatever service_name you are using isn’t a valid service according to the DB.

(*I was running sqlplus from Win7 client workstation to remote DB and blame the DBAs 😉 *)