1、停止数据库

SQL> shutdown immediate;   

2、启动数据库mount，

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; 

3、启动数据库

SQL> alter database open; 

4、修改字符集

SQL> ALTER DATABASE CHARACTER SET ZHS16GBK; 
ALTER DATABASE CHARACTER SET ZHS16GBK
*
ERROR at line 1:
ORA-12712: new character set must be a superset of old character set


SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK; 

Database altered.

5、重新启动数据库

SQL> shutdown immediate; 
SQL> startup 

6、查询oracle server端字符集

SQL> select userenv ('language')  from dual;

USERENV('LANGUAGE')
----------------------------------------------------
AMERICAN_AMERICA.ZHS16GBK