Oracle 11g modified character set to ZHS16GBK

Method One: Sqlplus "user/password as SYSDBA" Sqlplus "Sys/sys as SYSDBA"
Method Two: Sqlplus/nolog

Sql> Conn/as SYSDBA
sql> shutdown immediate;
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 ZHS16GBK;
Ora-12712:new character set must be a superset of the old character set
Hint to our character set: The new character set must be a superset of the old character set, and we can skip over the superset check to make the change:
Sql> ALTER DATABASE Character set Internal_use ZHS16GBK;
--we see that this process is identical to the internal procedure of the ALTER DATABASE CHARACTER set operation, which means that the help provided by Internal_use is to get the Oracle database to bypass the checksum of the subset and the superset.
sql> shutdown immediate;
Sql> Startup

Sql> Select Userenv (' language ') from dual; Oracle View Character Set