RAC环境下的阻塞(blocking blocked)

      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;

BANNER
--------------------------------------------------------------------------------
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;

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