To use internationalization features, your database should be created with NLS_NCHAR_CHARACTERSET set to AL16UTF16 or AL32UTF8. If it is set to AL32UTF8, a conversion between UTF-16 and UTF-8 encodings is initiated on the server side.

All data passed to and read back from the DB Access Module for Oracle OCI with Oracle datatypes NCHAR and NVARCHAR2 should be in UTF-16 encoding.