Oracle modifies the character set of a database instance

Run the following commands in sqlplus:

Connect system as sysdba; -- Be sure to log in as DBA; otherwise, an error will be reported below
Shutdown immediate; -- this is to disable the session currently connected to the database. If a session is connected to the database, changing the character set is not allowed.
Startup Mount; -- restart
Alter system enable restricted session; -- disable normal user logon
Alter system set job_queue_processes = 0;
Alter system set aq_tm_processes = 0;
Alter database open;
Alter database character set internal_use utf8; -- utf8 is the target character set zhs16gbk to be modified
Shutdown immediate;
Startup;