Oracle Connection Error Messages
A quick summary of what might go wrong when trying to connect to an Oracle database. Based on this excellent article. Read the whole thing, this is just a quick reference.
| Error Code | Message | Translation |
| ORA-12154 | TNS:could not resolve the connect identifier specified | No entry with the requested name in tnsnames.ora |
| ORA-12545 | Connect failed because target host or object does not exist | There is an entry in tnsnames.ora, but the hostname doesn’t resolve to an IP, or the IP is bad. The server can’t be reached |
| ORA-12541 | TNS:no listener | All the above are OK, but there is no listener process running on the server we’re trying to connect to |
| ORA-12560 | TNS:protocol adapter error | The connection to the server is OK, and there is a listener process on the target server, but it is running on a different port than that specified in the tnsnames.ora |
| ORA-12514 | TNS:listener does not currently know of service requested in connect descriptor/td> | We got as far as connecting to the listener process on the server, but the service name in the tnsnames.ora is wrong |