Oracle ORA-12154: TNS: Could not resolve service name Error?

from http://ora-12154.ora-code.com

ORA-12154: TNS:could not resolve the connect identifier specified
Cause: A connection to a database or other service was requested using a connect identifier, and the connect identifier specified could not be resolved into a connect descriptor using one of the naming methods configured. For example, if the type of connect identifier used was a net service name then the net service name could not be found in a naming method repository, or the repository could not be located or reached.
Action:

• If you are using local naming (TNSNAMES.ORA file):

• Make sure that "TNSNAMES" is listed as one of the values of the NAMES.DIRECTORY_PATH parameter in the Oracle Net profile (SQLNET.ORA)

• Verify that a TNSNAMES.ORA file exists and is in the proper directory and is accessible.

• Check that the net service name used as the connect identifier exists in the TNSNAMES.ORA file.

• Make sure there are no syntax errors anywhere in the TNSNAMES.ORA file. Look for unmatched parentheses or stray characters. Errors in a TNSNAMES.ORA file may make it unusable.

• If you are using directory naming:

• Verify that "LDAP" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).

• Verify that the LDAP directory server is up and that it is accessible.

• Verify that the net service name or database name used as the connect identifier is configured in the directory.

• Verify that the default context being used is correct by specifying a fully qualified net service name or a full LDAP DN as the connect identifier

• If you are using easy connect naming:

• Verify that "EZCONNECT" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).

• Make sure the host, port and service name specified are correct.

• Try enclosing the connect identifier in quote marks. See the Oracle Net Services Administrators Guide or the Oracle operating system specific guide for more information on naming.

Going on the assumption you're using TNSNAMES naming, here's a couple of things to do:

• Create/modify the tnsnames.ora file in the network/admin subdirectory associated with OraHome90 to include an entry for your oracle database:

> SERVICENAME_alias =>    (DESCRIPTION =>     (ADDRESS = (PROTOCOL = TCP)(HOST = HOST.XYZi.com)(PORT = 1521))>     (CONNECT_DATA = (SERVICE_NAME = SERVICENAME))

This is assuming you're using the standard Oracle port of 1521. Note that servicename_alias can be any name you want to use on the local system. You may also find that you need to specify (SID = SERVICENAME) instead of (SERVICENAME=SERVICENAME).

• Execute tnsping servicename_alias to verify connectivity. Get this working before going any further. This will tell you if you're past the 12154 error.
• Assuming a good connection, create an ODBC DSN using the control panel, specifying the ODBC driver for Oracle of your choice (generally there's a Microsoft ODBC driver at least, and it should work adequately as a proof of concept). I'll assume the name you gave of DATASOURCE. Use the servicename_alias as the Server name in the ODBC configuration.
• At this point you should be able to connect to your database via Access. I am not a VB programmer, but I know you should be able to go to File->Get External Data->Link Tables and connect to your ODBC source. I would assume your code would work as well.

In reference to #7 in this MSDN POST , adding a registry entry worked for me. I had Vs2010, et oracle 11.0 installed.

Check for the registry key “TNS_ADMIN” at HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE. If it exists then make sure it has the right value as “Dir:\app\product\11.1.0\client_1\network\admin”. If you don’t see the key then create the key and set appropriate value as below. Regedit->HKEY_LOCAL_MACHINE->Software->Oracle->RightClick NEW->StringValue and name it TNS_ADMIN and give the value “X:\app\product\11.1.0\client_1\network\admin”