Changing Oracle Database Character Set to Arabic

Normally, Character Set is defined at Database Creation.  Changing the character set of the database to a subset of the original character set (set from the same family, ie Different flavour of Arabic) is supported.

However, changing the database character set among different radically different character sets is not supports (From ASCII to Arabic , or From Western European to Arabic) is NOT supported

Still, Nevertheless, Oracle provided (non documented) technique to do such conversion. The technique is not supported, and should be carried out at your own RISK (Take a backup before you start)

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER SYSTEM ENABLE RESTRICTED SESSION;
ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
ALTER SYSTEM SET AQ_TM_PROCESSES=0;
ALTER DATABASE OPEN;
ALTER DATABASE CHARACTER SET INTERNAL_USE AR8MSWIN1256;
SHUTDOWN IMMEDIATE;