-------------------查看当前有哪些用户正在使用数据
SELECT osuser, a.username,cpu_time/executions/1000000||‘s‘, sql_fulltext,machine
from v$session a, v$sqlarea b
where a.sql_address =b.address order by cpu_time/executions desc;

--------------------查询是什么SQL引起了锁表的原因
select l.session_id sid,
       s.serial#,
       l.locked_mode,
       l.oracle_username,
       s.user#,
       l.os_user_name,
       s.machine,
       s.terminal,
       a.sql_text,
       a.action
  from v$sqlarea a, v$session s, v$locked_object l
where l.session_id = s.sid
   and s.prev_sql_addr = a.address
order by sid, s.serial#;

--------------------查看被锁对象和解锁方法
（1）被锁对象
select   a.SID, a.SERIAL#, c.object_name, b.oracle_username,b.os_user_name
from 
       v$session         a,        
       v$locked_object   b,
       v$process         p,
       all_objects       c
where     
        a.process=b.process   and
        a.paddr=p.addr   and 
        b.object_id= c.object_id;

锁(上)