How to modify the Oracle Data Character Set

Select distinct (nls_charset_name (charsetid) characterset,
Decode (type #,
1,
Decode (charsetform,
1,
'Varchar2 ',
2,
'Varchar2 ',
'Unkown '),
9,
Decode (charsetform,
1,
'Varchar ',
2,
'Nchar vary ',
'Unkown '),
96,
Decode (charsetform, 1, 'Char ', 2, 'nchar', 'unkown '),
112,
Decode (charsetform, 1, 'clob', 2, 'clob', 'unkown ') types_used_in
From SYS. Col $
Where charsetform in (1, 2)
And type # In (1, 9, 96,112 );

Modify the value of nls_characterset and nls_nchar_characterset in the SYS. Props $ table to utf8.

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;

Col value new_value charset
Select value from nls_database_parameters where parameter = 'nls _ characterset ';
Col value new_value ncharset
Select value from nls_database_parameters where parameter = 'nls _ nchar_characterset ';

Alter database character set internal_use & charset;
Alter database National Character Set internal_use & ncharset;

Shutdown immediate;
Startup;

Shutdown immediate;
Startup;