Use alter database charset FOR INTERNAL USE at your own risk. Contrary to advice given above, changing character sets can leave your database corrupted. Oracle states that they will not support a database that has had the FOR INTERNAL USE option applied. As you might guess, that option is supposed to be known to Oracle personnel only. If you really know what you're doing and you've run the character scanner (and it reports no potential problems) then you can use that at your own risk. But I'd be sure that I had a working backup of the database before I tried it.