Changing the Oracle Character Set after installation

Sometimes when creating an Oracle Database, we forget to choose the correct character set on the relevant dbca screen. Then, when we then go to import data or create data we discover that the character set is not correct. With Oracle 11g, you can actually change it after the database creation. Here is sql plus commands to make this happen:

conn / as sysdba
-------
SHUTDOWN IMMEDIATE;
STARTUP RESTRICT;
ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
ALTER SYSTEM SET AQ_TM_PROCESSES=0;
-------
ALTER DATABASE CHARACTER SET EL8ISO8859P7;
--- EL8ISO8859P7 is greek

-- if the above fails:
ALTER DATABASE CHARACTER SET INTERNAL_USE EL8ISO8859P7;
SHUTDOWN IMMEDIATE;
STARTUP;
 
---if all this is not working run the following command to reload the stylesheet
dbms_metadata_util.load_stylesheets