Character Set Migration

Take Full export of database before starting this activity.

1. Do a full backup via export or RMAN
2. SHUTDOWN IMMEDIAT;
3. STARTUP MOUNT;
4. ALTER SYSTEM ENABLE RESTRICTED SESSION;
5. ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
7. ALTER DATABASE OPEN;
8. ALTER DATABASE CHARACTER SET AL32UTF8;

I got error at step 8:

SQL> ALTER DATABASE CHARACTER SET AL32UTF8;
ALTER DATABASE CHARACTER SET AL32UTF8
*
ERROR at line 1:
ORA-12712: new character set must be a superset of old character set

We need to make sure New character set would be superset of old characterset , check below link for checking super set

alternatively used

ALTER DATABASE CHARACTER SET INTERNAL_USE AL32UTF8;

This command does not the check whether character set is a subset or superset.

9. SHUTDOWN IMMEDIATE;
10. STARTUP;