Character sets for an existing oracle 10g instance

[savourys]

I need to change an existing db to be displayed using unicode character set (i.e. polish) but not affect the english data that is contained in the db.

any ideas? This is not my forte.

[pss]

Two possible solutions:

1) Use NVARCHAR2 columns to store the data (application may need to be aware of this)

2) Create a new instance as unicode and migrate the data over. First 128 ASCII characters will remain the same.

I think there is a way to convert in place but I never used it myself. Generally, I don't like converting things. It may bite you later in the process real bad way. Be careful with character column sizes (bytes vs chars).

[Bore]

Which characterset you currently use? If that's a subset of UTF8 you will be able simply to change the characterset using
alter database set character set ='UTF8'

[savourys]

we are currently using we8mswin1252 and need to change to UTF8.

Created a new instance and tried an import but the import terminated with warnings about some of the columns containing too many characters.

crap!

[Bore]

The warning is because UTF8 is multinyte character set and hence some columns should be extended. Make a list of these columns, make a script to extend them and go again