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.