Oracle RAC环境下的阻塞(blocking blocked)介绍和实例演示

rac环境下的阻塞不同于单实例情形，因为我们需要考虑到位于不同实例的session。也就是说之前查询的v$session，v$lock相应的应变化为全局范围来查找。本文提供了2个查询脚本，并给出实例演示那些session为阻塞者，哪些为被阻塞者。有关阻塞的概念以及单实例环境下的阻塞请参考：oracle 阻塞(blocking blocked)

1、演示环境

scott@devdb> select * from v$version where rownum<2;

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oracle database 11g enterprise edition release 11.2.0.3.0 - 64bit production

--在scott session中发布sql语句，并未提交
scott@devdb> begin
 2 update emp set sal=sal+100 where empno=7788;
 3 update dept set dname='dba' where deptno=10;
 4 end;
 5 /

pl/sql procedure successfully completed.

--在leshami session中更新emp对象
leshami@devdb> update scott.emp set sal=sal-200 where empno=7788;

--在usr1 session中更新emp对象
usr1@devdb> update scott.dept set dname='dev' where deptno=10;

2、寻找阻塞

scott@devdb> @block_session_rac

user_status   sid_serial   conn_instance   sid program            osuser machine     lock_type    lock_mode    ctime object_name
--------------- --------------- ---------------- ---- ------------------------------ ------- --------------- --------------- ----------- ---------- -------------------------
blocking ->   '20,1545'    devdb1       20 sqlplus@linux-01 (tns v1-v3)  oracle linux-01    transaction   exclusive     666 dept
blocking ->   '20,1545'    devdb1       20 sqlplus@linux-01 (tns v1-v3)  oracle linux-01    transaction   exclusive     666 emp
waiting     '49,1007'    devdb1       49 sqlplus@linux-01 (tns v1-v3)  oracle linux-01    transaction   none        618 emp
waiting     '933,11691'   devdb2      933 sqlplus@linux-02 (tns v1-v3)  oracle linux-02    transaction   none        558 dept

--通过上述脚本我们可以看到session '20,1545' 锁住了对象dept以及emp，而此时session '49,1007'与'933,11691'处于等待状态。

--下面是另外的一种方式来获取阻塞的情形
scott@devdb> @block_session_rac2

blocking_status
----------------------------------------------------------------------------------------------------------------------------
scott@linux-01 ( inst=1 sid=20 serail#=1545 ) is blocking usr1@linux-02 ( inst=2 sid=933 serial#=11691 )
scott@linux-01 ( inst=1 sid=20 serail#=1545 ) is blocking leshami@linux-01 ( inst=1 sid=49 serial#=1007 )

--author : leshami
--blog  : http://blog.csdn.net/leshami

3、演示中用到的脚本

[oracle@linux-01 ~]$ more block_session_rac.sql 
set linesize 180
col user_status format a15
col sid_serial format a15
col program format a30 wrapped
col machine format a15 wrapped
col osuser format a15 wrapped
col conn_instance format a15
col object_name format a25 wrapped
 select decode (l.block, 0, 'waiting', 'blocking ->') user_status,
     chr (39) || s.sid || ',' || s.serial# || chr (39) sid_serial,
     (select instance_name
      from gv$instance
      where inst_id = l.inst_id)
      conn_instance,
     s.sid,
     s.program,
     s.osuser,
     s.machine,
     decode (l.type,
         'rt', 'redo log buffer',
         'td', 'dictionary',
         'tm', 'dml',
         'ts', 'temp segments',
         'tx', 'transaction',
         'ul', 'user',
         'rw', 'row wait',
         l.type)
      lock_type--,id1
           --,id2
     ,
     decode (l.lmode,
         0, 'none',
         1, 'null',
         2, 'row share',
         3, 'row excl.',
         4, 'share',
         5, 's/row excl.',
         6, 'exclusive',
         ltrim (to_char (lmode, '990')))
      lock_mode,
     ctime--,decode(l.block, 0, 'not blocking', 1, 'blocking', 2, 'global') lock_status
     ,
     object_name
  from gv$lock l
     join gv$session s on (l.inst_id = s.inst_id and l.sid = s.sid)
     join gv$locked_object o
      on (o.inst_id = s.inst_id and s.sid = o.session_id)
     join dba_objects d on (d.object_id = o.object_id)
  where (l.id1, l.id2, l.type) in (select id1, id2, type
                   from gv$lock
                   where request > 0)
order by id1, id2, ctime desc;

[oracle@linux-01 ~]$ more block_session_rac2.sql 
select distinct
     s1.username
    || '@'
    || s1.machine
    || ' ( inst='
    || s1.inst_id
    || ' sid='
    || s1.sid
    || ' serail#='
    || s1.serial#
    || ' ) is blocking '
    || s2.username
    || '@'
    || s2.machine
    || ' ( inst='
    || s2.inst_id
    || ' sid='
    || s2.sid
    || ' serial#='
    || s2.serial#
    || ' ) '
     as blocking_status
 from gv$lock l1,
    gv$session s1,
    gv$lock l2,
    gv$session s2
 where   s1.sid = l1.sid
    and s2.sid = l2.sid
    and s1.inst_id = l1.inst_id
    and s2.inst_id = l2.inst_id
    and l1.block > 0
    and l2.request > 0
    and l1.id1 = l2.id1
    and l1.id2 = l2.id2;