Database Software

I'm working on a version 11.2 database with

NLS_CHARACTERSET = WE8MSWIN1252
and
NLS_NCHAR_CHARACTERSET = AL16UTF16

I've got some UFT8 characters being sent to the database as raw data. I need to be able to store this in a readable format and I think the only option is an NVarchar2 column.

I think the solution should include something like this:

      utl_raw.cast_to_nvarchar2(
      utl_raw.convert(
         r            => <raw data>,
         to_charset   => 'AL16UTF16',
         from_charset => 'UTF8'))

but that gives me an exception: ORA-06502: PL/SQL: numeric or value error


Also, am I right in thinking that any Varchar2 column in this database can only hold single-byte characters (from WE8MSWIN1252) even if the size is defined as "n char"?


I've not worked much with different character sets so any help would be appreciated. Thanks.