Database Software

I'm getting different results from Java's toLowerCase() function compared with Oracle's lower. Specifically it appears that in a windows-1252 DB the latin capital letter Z with caron does not get lowercased to it's equivalent (but does in Java):

Ž (142) --> ž (158)

Also, in a windows-1251 DB the cyrillic capital letter ghe with upturn does not get lowercased to it's equivalent (but does in Java):

Ґ (165) --> ґ (180)

Using Locale builder I can create a new characters set which is based on windows-1251 or 1252 and add the correct lower and upper case mappings, however I would like to modify the existing character set definition to include the new mapping. Anyone have any ideas?

Is it possible to add a new lower to upper case / upper to lower case mapping to an existing character set (such as windows-1252 or 1251)?

Thanks!