EXP-00091: Exporting questionable statistics.

When exporting tables if raise an error like below

EXP-00091: Exporting questionable statistics.

cause : incomplete NLS_LANG character set between client and server.

solution : you must set NLS_LANG parameter client side which compatible to server character set.



query NLS_CHARACTERSET parameter of db

SQL> col value format a40 
SQL> select * from nls_database_parameters where parameter = 'NLS_CHARACTERSET';

PARAMETER                      VALUE
------------------------------ ----------------------------------------
NLS_CHARACTERSET               AL32UTF8

You can set set NLS_LANG like below

set NLS_LANG=AMERICAN_AMERICA.AL32UTF8




Actually the important section of NLS_LANG is AL32UTF8. you can set your localization values before dot (.)
e.g:

set NLS_LANG=TURKISH_TURKEY.AL32UTF8