SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount# 进入维护模式
ORACLE instance started.
Total System Global Area 4275781632 bytes
Fixed Size 2260088 bytes
Variable Size 905970568 bytes
Database Buffers 3355443200 bytes
Redo Buffers 12107776 bytes
Database mounted.
SQL> alter system enable restricted session;# 在维护模式的基础上再开启 restricted,防止其他用户登录连接
System altered.
SQL> alter system set job_queue_processes=0;# 关闭系统的触发器
System altered.
SQL> alter system set aq_tm_processes=0;# 指定队列监视进程个数,缺省是 0,如果没有改过可以不加
System altered.
SQL> alter database open;# 打开数据库
Database altered.
SQL> alter database character set internal_use al32utf8;# 进行字符集修改
Database altered.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup# 最后重启修改字符集生效
ORACLE instance started.
Total System Global Area 4275781632 bytes
Fixed Size 2260088 bytes
Variable Size 905970568 bytes
Database Buffers 3355443200 bytes
Redo Buffers 12107776 bytes
Database mounted.
Database opened.
来源: http://www.linuxidc.com/Linux/2017-12/149915.htm