Modify the character set of Oracle 11g to ZHS16GBK

Method 1: sqlplus "User/password as sysdba" sqlplus "sys/sys as sysdba"
Method 2: 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 old character set
Note: The new character set must be a superset of the old one. In this case, we can skip the superset check and make changes:
SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK;
-- We can see that this process is exactly the same as the internal process of the alter database character set operation. That is to say, the help provided by INTERNAL_USE is that the Oracle DATABASE bypasses the validation of the subset and superset.
SQL> shutdown immediate;
SQL> startup

SQL> select userenv ('language') from dual; Oracle view Character Set