Oracle server returns this error if you specified incorrect name of database.
‘The TNS-12154 error is encountered when SQL*Net cannot find the alias specified for a connection in the TNSNAMES.ORA file or other naming adapter.
Before attempting to resolve the problem, it may be helpful to have a print out or view of both the TNSNAMES.ORA file and the SQLNET.ORA file. Looking at these files at the same time is helpful since references will be made to both.’
Note: ‘Host and port are ignored if net service name is used’ definition means that you can omit corresponding fields filling if you have an Oracle client installed on your computer. For this example we used ORAClient10g (10.2.0).