Keep the following restrictions in mind when you are using direct path mode:
To start a direct path Export, you must use either the command-line method or a parameter file. You cannot start a direct path Export using the interactive method.
The Export parameter BUFFER applies only to conventional path Exports. For direct path Export, use the RECORDLENGTH parameter to specify the size of the buffer that Export uses for writing to the export file.
You cannot use direct path when exporting in tablespace mode (TRANSPORT_TABLESPACES=Y).
The QUERY parameter cannot be specified in a direct path Export.
A direct path Export can only export data when the NLS_LANG environment variable of the session invoking the export equals the database character set. If NLS_LANG is not set or if it is different than the database character set, then a warning is displayed and the export is discontinued. The default value for the NLS_LANG environment variable is AMERICAN_AMERICA.US7ASCII.