Hi.
I'm writing this, because I didn't find nothing usefull over internet, but I manage to resolve my situation.
Our DB has set default NLS_CHARSET to EE8MSWIN1250 (Windows-1250). I daily recieve xml files with AL32UTF8 (UTF-8) encoding, so I have to convert from one to another charset to get correct (special) characters.
I have tabel with more than one column, one of them is column of xmltype (STORE AS SECUREFILE BINARY XML).
The solution. You can use following call for select, update or insert: xmltype(convert((xml_column_name).getClobVal(),'EE8MSWIN1250','AL32UTF8'))
Maybe is nothing special when You see It, but I spent too much time to solve It, so I decided to share.
Sincerely, B.