oracle11g change Character Set Al32utf8 to Zhs16gbk__oracle

The Database character set (Al32utf8) and Client character set (ZHS16GBK) are different.
Character set conversion may cause unexpected results.
Note:you can set the client character set through the Nls_lang environment variable or the Nls_lang key in
Hkey_local_machine/software/oracle/key_oradb11g_home

Simplified Chinese_china. ZHS16GBK contains American_america. Al32utf8.
It's a hassle, not a problem with changing the client character set. To change the character set of the database:
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 is a superset of old character set
Tip Our Character set: The new character set must be a superset of the old character set, at which point we can skip the check of the superset to make changes:
Sql> ALTER DATABASE Character set Internal_use ZHS16GBK;
--we see that this process is exactly the same as the internal process of an ALTER DATABASE CHARACTER set operation, meaning that the help that Internal_use provides is that the Oracle database bypasses the checksum of subsets and superset.
Sql> select * from V$nls_parameters;
sql> shutdown immediate;
Sql> Startup
Sql> select * from V$nls_parameters;
When installing oracle11g later, remember to choose Custom installation, the character set of things in advance