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 registry key in 
HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OraDb11g_home1. 

SIMPLIFIED CHINESE_CHINA.ZHS16GBK 包含 AMERICAN_AMERICA.AL32UTF8. 
-- 这可是个麻烦事，不是改客户端字符集的问题。要改数据库的字符集。
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 
--提示我们的字符集：新字符集必须为旧字符集的超集，这时我们可以跳过超集的检查做更改： 
SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK; 
--我们看到这个过程和之前ALTER DATABASE CHARACTER SET操作的内部过程是完全相同的，也就是说INTERNAL_USE提供的帮助就是使Oracle数据库绕过了子集与超集的校验. 
SQL> select * from v$nls_parameters;  
SQL> shutdown immediate; 
SQL> startup 
SQL> select * from v$nls_parameters; 
--以后安装oracle11g的时候记得选择自定义安装，把这个字符集的事情事先弄好。

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