CHANGING characterset

Hi all,

I need to change the NLS_NCHAR_CHARACTERSET from AL16UTF16 to WE8ISO8859P1 in my new 11g database. Can you please show me the steps on how to do it. I cant find the documents on this.

Hope someone will be able to help me to change this

select PARAMETER||' '||VALUE from V$NLS_PARAMETERS where PARAMETER like '%CHARACTER%';

NLS_CHARACTERSET WE8ISO8859p1

NLS_NCHAR_CHARACTERSET AL16UTF16

Thanks