Oracle characterset

Dear Sirs, Have you used Oracle 8 or Oracle 8i with another character set than US7ASCII and maked it work well? We're trying to use the Greek characterset. But I've also tried the portuguese one. In both cases, didn't work. For the both languages the only characterset that is working well is the US7ASCII. But if I use this, the UPPER() function of Oracle don't works well. I think that the US7ASCII is working with these languages bacause only the first 127 characters are really defibned on it. But I can't understando why the others charactersets, that are supposed to work, are not working? If anyone could help us, that will be nice! Thanks! Andre.