ORA-12705: Cannot access NLS data files or invalid environment specified

It can be resolved by the following methods:

• check your oracle xe database settings by executing this in sqlplus:

         select userenv('LANGUAGE') from dual;

         For example, the result of this query can be ENGLISH_AMERICA.WE8MSWIN1252)

• change your regional settings in control panel according to your database

         (For this example it can be changed to English (United States))

• change NLS parameters in sql developer according to your database and regional settings (in sql developer tools/preferences/database/NLS Parameters, you need to select english language, american territory and pressed default values for the rest of the fields)
• don't forget to restart your computer for this to take effect

Screenshot below shows correct connection parameters:

We advise you to specify ‘SYSTEM’ schema as default one because ‘ANONYMOUS’ schema allows only to read database. It is more important if you need to specify an Oracle schema for destination. But the most preferable method is to choose your own connection schema pre-created on Oracle server especially for your work.

Accordingly, Oracle server configurations for the connection parameters shown above look the way presented here:

For more information regarding Troubleshooting Oracle Net Services please visit Oracle web site