先用sqlplus 系统用户登录：
sqlplus / as sysdba;
然后执行下面的命令即可：
shutdown immediate; //关闭数据库服务器
startup mount;
alter session set sql_trace=true;
alter system enable restricted session;
alter system set job_queue_processes=0;
alter system set aq_tm_processes=0;
alter database open;
alter database character set internal_use utf8;
alter session set sql_trace=false;
shutdown immediate;
startup;