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
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scott@DEVDB> select * from v$version where rownum<2;
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BANNER
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--------------------------------------------------------------------------------
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Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
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--在scott session中发布SQL语句，并未提交
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scott@DEVDB> begin
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2 update emp set sal=sal+100 where empno=7788;
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3 update dept set dname='DBA' where deptno=10;
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4 end;
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5 /
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PL/SQL procedure successfully completed.
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--在leshami session中更新emp对象
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leshami@DEVDB> update scott.emp set sal=sal-200 where empno=7788;
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--在usr1 session中更新emp对象
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usr1@DEVDB> update scott.dept set dname='DEV' where deptno=10;
2、寻找阻塞
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scott@DEVDB> @block_session_rac
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USER_STATUS SID_SERIAL CONN_INSTANCE SID PROGRAM OSUSER MACHINE LOCK_TYPE LOCK_MODE CTIME OBJECT_NAME
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--------------- --------------- ---------------- ---- ------------------------------ ------- --------------- --------------- ----------- ---------- -------------------------
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Blocking -> '20,1545' devdb1 20 sqlplus@Linux-01 (TNS V1-V3) oracle Linux-01 Transaction Exclusive 666 DEPT
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Blocking -> '20,1545' devdb1 20 sqlplus@Linux-01 (TNS V1-V3) oracle Linux-01 Transaction Exclusive 666 EMP
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Waiting '49,1007' devdb1 49 sqlplus@Linux-01 (TNS V1-V3) oracle Linux-01 Transaction None 618 EMP
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Waiting '933,11691' devdb2 933 sqlplus@Linux-02 (TNS V1-V3) oracle Linux-02 Transaction None 558 DEPT
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--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。
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--下面是另外的一种方式来获取阻塞的情形
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scott@DEVDB> @block_session_rac2
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BLOCKING_STATUS
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----------------------------------------------------------------------------------------------------------------------------
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SCOTT@Linux-01 ( INST=1 SID=20 Serail#=1545 ) IS BLOCKING USR1@Linux-02 ( INST=2 SID=933 Serial#=11691 )
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SCOTT@Linux-01 ( INST=1 SID=20 Serail#=1545 ) IS BLOCKING LESHAMI@Linux-01 ( INST=1 SID=49 Serial#=1007 )
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--Author : Leshami
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--Blog : http://blog.csdn.net/leshami
3、演示中用到的脚本
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[oracle@Linux-01 ~]$ more block_session_rac.sql
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set linesize 180
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col user_status format a15
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col sid_serial format a15
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col program format a30 wrapped
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col machine format a15 wrapped
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col osuser format a15 wrapped
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col conn_instance format a15
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col object_name format a25 wrapped
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SELECT DECODE (l.block, 0, 'Waiting', 'Blocking ->') user_status,
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CHR (39) || s.sid || ',' || s.serial# || CHR (39) sid_serial,
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(SELECT instance_name
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FROM gv$instance
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WHERE inst_id = l.inst_id)
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conn_instance,
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s.sid,
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s.program,
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s.osuser,
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s.machine,
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DECODE (l.TYPE,
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'RT', 'Redo Log Buffer',
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'TD', 'Dictionary',
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'TM', 'DML',
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'TS', 'Temp Segments',
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'TX', 'Transaction',
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'UL', 'User',
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'RW', 'Row Wait',
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l.TYPE)
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lock_type--,id1
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--,id2
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,
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DECODE (l.lmode,
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0, 'None',
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1, 'Null',
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2, 'Row Share',
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3, 'Row Excl.',
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4, 'Share',
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5, 'S/Row Excl.',
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6, 'Exclusive',
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LTRIM (TO_CHAR (lmode, '990')))
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lock_mode,
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ctime--,DECODE(l.BLOCK, 0, 'Not Blocking', 1, 'Blocking', 2, 'Global') lock_status
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,
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object_name
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FROM gv$lock l
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JOIN gv$session s ON (l.inst_id = s.inst_id AND l.sid = s.sid)
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JOIN gv$locked_object o
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ON (o.inst_id = s.inst_id AND s.sid = o.session_id)
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JOIN dba_objects d ON (d.object_id = o.object_id)
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WHERE (l.id1, l.id2, l.TYPE) IN (SELECT id1, id2, TYPE
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FROM gv$lock
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WHERE request > 0)
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ORDER BY id1, id2, ctime DESC;
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[oracle@Linux-01 ~]$ more block_session_rac2.sql
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SELECT DISTINCT
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s1.username
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|| '@'
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|| s1.machine
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|| ' ( INST='
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|| s1.inst_id
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|| ' SID='
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|| s1.sid
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|| ' Serail#='
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|| s1.serial#
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|| ' ) IS BLOCKING '
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|| s2.username
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|| '@'
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|| s2.machine
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|| ' ( INST='
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|| s2.inst_id
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|| ' SID='
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|| s2.sid
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|| ' Serial#='
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|| s2.serial#
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|| ' ) '
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AS blocking_status
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FROM gv$lock l1,
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gv$session s1,
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gv$lock l2,
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gv$session s2
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WHERE s1.sid = l1.sid
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AND s2.sid = l2.sid
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AND s1.inst_id = l1.inst_id
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AND s2.inst_id = l2.inst_id
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AND l1.block > 0
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AND l2.request > 0
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AND l1.id1 = l2.id1
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AND l1.id2 = l2.id2;
