1.(Window：)cmd下输入set ORACLE_SID=你想进入的数据库的那个sid

(Linux：)切换到oracle用户：export  ORACLE_SID=你想进入的数据库的那个sid

2.输入 sqlplus /nolog

3.将数据库启动到RESTRICTED模式下做字符集更改：

SQL> conn /as sysdba

Connected.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL>startup mount

ORACLE instance started.

Total System Global Area  236000356 bytes

Fixed Size                   451684 bytes

Variable Size             201326592 bytes

Database Buffers           33554432 bytes

Redo Buffers                 667648 bytes

Database mounted.

SQL>ALTER SYSTEM ENABLE RESTRICTED SESSION;

System altered.

SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;

System altered.

SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;

System altered.

SQL> alter database open;

Database altered.

--修改为中文字符集

SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK;

--修改为英文字符集

SQL> ALTER DATABASE character set INTERNAL_USE  AL32UTF8;

Database altered.

SQL>select * from v$nls_parameters;

略

19 rows selected.

重启检查是否更改完成：

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

Total System Global Area  236000356 bytes

Fixed Size                   451684 bytes

Variable Size             201326592 bytes

Database Buffers           33554432 bytes

Redo Buffers                 667648 bytes

Database mounted.

Database opened.

SQL> select * from v$nls_parameters;