oracle等待事件实验--enq: TX - row lock contention

      oracle10g等待事件很多，看资料往往过于理论，不太容易记住。打算对常用的等待事件做实验重现，并能运用到实际的工作中解决问题。

--创建表，插入数据
create table tx_lock_tab(a number,b char(1), c varchar2(20));
insert into tx_lock_tab(a,b,c) values(99,'c','aaa');
insert into tx_lock_tab(a,b,c) values(100,'c','aaa');
insert into tx_lock_tab(a,b,c) values(101,'c','aaa');

commit;
--在session1中删除
delete from tx_lock_tab where a=100;
--在session2中删除
delete from tx_lock_tab where a=100;

--查看锁队列
select * from v$enqueue_lock where type='TX';
--等待事件
select s.sid,s.event from v$session_event s,v$enqueue_lock l
where s.sid =l.SID
and s.EVENT like 'enq: TX%';
--查看对应的sql
select distinct w.waiting_session,
                s2.USERNAME waiting_user,
                q2.SQL_TEXT waiting_sql
  from dba_waiters w, v$session s2, v$sqlarea q2
 where w.waiting_session = s2.SID
   and s2.SQL_ADDRESS = q2.ADDRESS;
--通过等待事件找到具体的数据   
select s.sid,
       o.object_name wait_object,
       s.row_wait_obj#,
       s.ROW_WAIT_FILE#,
       s.ROW_WAIT_BLOCK#,
       s.ROW_WAIT_ROW#,
       dbms_rowid.rowid_create(1,
                               s.row_wait_obj#,
                               s.ROW_WAIT_FILE#,
                               s.ROW_WAIT_BLOCK#,
                               s.ROW_WAIT_ROW#) l_rowid
  from v$session s, v$enqueue_lock l,dba_objects o
 where s.sid = l.SID
   and s.ROW_WAIT_OBJ# = o.object_id(+)
   and s.SID = 156;
select * from tx_lock_tab where rowid = 'AAAT+FAAGAAAcy+AAD';
--等待事件，等待sql及耗时时长  
select s.sid, s.event, s.seconds_in_wait, q.sql_text
  from v$session s, v$sqlarea q
 where s.SQL_ADDRESS = q.ADDRESS(+)
   and s.SQL_HASH_VALUE = q.HASH_VALUE(+)
   and s.SID = 156;    
    生成ASH报告，可以在Top Events中看到，这种问题往往是业务逻辑代码不合理。