How to change oracle database character set?

This article gives a overview of methods to change the database character set .

1. Check NLS_CHARACTERSET
Connect to user SYS or SYSTEM

SELECT *
FROM V$NLS_PARAMETERS
WHERE PARAMETER = 'NLS_CHARACTERSET';

Parameter                                         Value
NLS_CHARACTERSET         WE8MSWIN1252

If you want to change NLS_CHARACTERSET from WE8MSWIN1252 to AL32UTF8

2. Connect to user SYS

3. Update value

UPDATE PROPS$
SET VALUE$ = 'AL32UTF8'
WHERE NAME = 'NLS_CHARACTERSET';

COMMIT;

4. Restart database

SHUTDOWN IMMEDIATE;

STARTUP;

5. Check NLS_CHARACTERSET
Connect to user SYS or SYSTEM

SELECT * FROM
V$NLS_PARAMETERS
WHERE PARAMETER = 'NLS_CHARACTERSET';

Parameter                                   Value
NLS_CHARACTERSET         AL32UTF8