ORA-12514 ORA-12528 - Trying a ALTER DATABASE CHARACTER SET

  10.2.0.1.0, Windows 2000,
Actually I wanted to

alter database character set WE8MSWIN1252;
	


following a recipe I found in some Wiki http://de.wikibooks.org/wiki/Oracle:_CharacterSet_ändern
	

sqlplus "sys/password@myDB as sysdba"
	
select value from nls_database_parameters where parameter='NLS_CHARACTERSET';
	
select * from nls_database_parameters;
	
shutdown immediate;
	
startup mount;
	
alter system enable restricted session;
	
alter system set job_queue_processes=0;
	
alter database character set UTF8;
	
ORA-12712: Der neue Zeichensatz muss eine Obermenge des alten Zeichensatzes
	
sein
	
alter database character set internal_use utf8;
	
shutdown immediate;
	
startup;
	
select * from nls_database_parameters;
	

(In my case I want to change an instance from UTF8 to WE8MSWIN1252, hoping it would work also the other way around)