SELECT * 
  FROM dba_users_with_defpwd d, 
       dba_users             du 
 WHERE du.account_status = 'OPEN' AND du.username = d.username;

在SQL*Plus中执行如下命令：  
SQL> connect/as sysdba (也可以以如下方式连接：SQL>connect internal)  
SQL> alter user sys identified by sys; (回车后用户sys的密码会更改为sys)   
SQL> alter user scott account unlock;（解锁命令）