Character Set Change

--------------Steps to change the database character set------------

To change the database character set, perform the following steps:

1. Shut down the database, using either a SHUTDOWN IMMEDIATE or a SHUTDOWN NORMAL statement.

2. Do a full backup of the database because the ALTER DATABASE CHARACTER SET statement cannot be rolled back.

3. Startup Oracle database

SQL> startup mount;

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;

SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;

SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;

SQL> ALTER DATABASE OPEN;

SQL> ALTER DATABASE CHARACTER SET AL32UTF8;

If you get the error ORA-12712, please update the following table.

"ORA-12712: new character set must be a superset of old character set"

SQL> update sys.props$ set VALUE$='AL32UTF8' where NAME='NLS_CHARACTERSET';

SQL> commit;

If you get the error ORA-12721, please login as DBA user.

"ORA-12721: operation cannot execute when other sessions are active"

4. shutdown immediate; or shutdown normal;

5. startup oracle database

SQL> startup mount;

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;

SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;

SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;

SQL> ALTER DATABASE OPEN;

SQL> ALTER DATABASE CHARACTER SET AL32UTF8;

select open_mode from v$database;

SQL> shutdown immediate;

SQL> startup;

--------------------Check the NLS parameters--------------------------

SQL> SELECT PARAMETER, VALUE FROM NLS_DATABASE_PARAMETERS WHERE PARAMETER IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET');