EXP-00056: ORACLE error 12714 encountered

When using export next errors may be shown:

EXP-00056: ORACLE error 12714 encountered

ORA-12714: invalid national character set specified

And your

NLS_NCHAR_CHARACTERSET is for example  US7ASCII, WE8ISO8859P1, CL8MSWIN1251
then you have to:

Change the tables to use CHAR, VARCHAR2 or CLOB instead the N-type

or
use export/import the table(s) containing N-type columns and truncate those tables before migrating to Oracle9i+

The recommended NLS_LANG during export is simply the NLS_CHARACTERSET,
not the NLS_NCHAR_CHARACTERSET
To check if there is such users that hace 'NCHAR' columns:

select distinct OWNER, TABLE_NAME from DBA_TAB_COLUMNS where
DATA_TYPE in ('NCHAR','NVARCHAR2', 'NCLOB') and OWNER not in
('SYS','SYSTEM');


Users with such columns are usually sample schemas instaled in database HR,OE,IX or HR8, OE8.....