Oracle 阻塞(blocking blocked)介绍和实例演示

--更新表，注，提示符scott@CNMMBO表明用户为scott的session，用户名不同，session不同。
scott@CNMMBO> update emp set sal=sal*1.1 where empno=7788;

1 row updated.

scott@CNMMBO> @my_env

SPID    SID SERIAL# USERNAME  PROGRAM
------------ ---------- ---------- --------------- ------------------------------------------------
11205    1073  4642 robin   oracle@SZDB (TNS V1-V3)

--另起两个session更新同样的行，这两个session都会处于等待，直到第一个session提交或回滚
leshami@CNMMBO> update scott.emp set sal=sal+100 where empno=7788;

goex_admin@CNMMBO> update scott.emp set sal=sal-50 where empno=7788;

--下面在第一个session 查询阻塞情况
scott@CNMMBO> @blocker 

BLOCK_MSG            BLOCK
-------------------------------------------------- ----------
pts/5 ('1073,4642') is blocking 1067,10438     1
pts/5 ('1073,4642') is blocking 1065,4464     1
--上面的结果表明session 1073,4642 阻塞了后面的2个
--即session 1073,4642是阻塞者，后面2个session是被阻塞者

--Author : Leshami
--Blog : http://blog.csdn.net/leshami

--下面查询正在阻塞的session id，SQL语句以及被阻塞的时间
scott@CNMMBO> @blocking_session_detail.sql

'SID='||A.SID||'WAITCLASS='||A.WAIT_CLASS||'TIME='||A.SECONDS_IN_WAIT||CHR(10)||'QUERY='||B.SQL_TEXT
-------------------------------------------------------------------------------------------------------
sid=1067 Wait Class=Application Time=5995
 Query=update scott.emp set sal=sal+100 where empno=7788

sid=1065 Wait Class=Application Time=225
 Query=update scott.emp set sal=sal-50 where empno=7788

--下面的查询阻塞时锁的持有情况 
scott@CNMMBO> @request_lock_type

USERNAME        SID TY LMODE  REQUEST   ID1  ID2
------------------------------ ---------- -- ----------- ----------- ---------- ----------
SCOTT        1073 TX Exclusive None   524319  27412
LESHAMI        1067 TX None  Exclusive  524319  27412
GOEX_ADMIN       1065 TX None  Exclusive  524319  27412
--可以看到LESHAMI，GOEX_ADMIN 2个用户都在请求524319/27412上的Exclusive锁，而此时已经被SCOTT加了Exclusive锁

--查询阻塞时锁的持有详细信息
scott@CNMMBO> @request_lock_detail

  SID USERNAME    OSUSER   TERMINAL     OBJECT_NAME   TY Lock Mode Req_Mode
---------- -------------------- --------------- ------------------------- -------------------- -- ----------- --------------------
  1065 GOEX_ADMIN   robin   pts/1      EMP     TM Row Excl
  1065 GOEX_ADMIN   robin   pts/1      Trans-524319   TX --Waiting-- Exclusive
  1067 LESHAMI    robin   pts/0      EMP     TM Row Excl
  1067 LESHAMI    robin   pts/0      Trans-524319   TX --Waiting-- Exclusive
  1073 SCOTT    robin   pts/5      EMP     TM Row Excl
  1073 SCOTT    robin   pts/5      Trans-524319   TX Exclusive 

robin@SZDB:~/dba_scripts/custom/sql> more my_env.sql 
SELECT spid, s.sid, s.serial#, p.username, p.program
FROM v$process p, v$session s
WHERE p.addr = s.paddr
  AND s.sid = (SELECT sid
     FROM v$mystat
     WHERE rownum = 1);

robin@SZDB:~/dba_scripts/custom/sql> more blocker.sql 
col block_msg format a50; 
select c.terminal||' ('''||a.sid||','||c.serial#||''') is blocking '||b.sid||','||d.serial# block_msg, a.block 
from v$lock a,v$lock b,v$session c,v$session d 
 where a.id1=b.id1 
 and a.id2=b.id2 
 and a.block>0
 and a.sid <>b.sid 
 and a.sid=c.sid 
 and b.sid=d.SID; 

robin@SZDB:~/dba_scripts/custom/sql> more blocking_session_detail.sql
--To find the query for blocking session

--Access Privileges: SELECT on v$session, v$sqlarea

SELECT  'sid='
   || a.SID
   || ' Wait Class='
   || a.wait_class
   || ' Time='
   || a.seconds_in_wait
   || CHR (10)
   || ' Query='
   || b.sql_text
 FROM v$session a, v$sqlarea b
 WHERE a.blocking_session IS NOT NULL AND a.sql_address = b.address
ORDER BY a.blocking_session
/
robin@SZDB:~/dba_scripts/custom/sql> more request_lock_type.sql
--This script generates a report of users waiting for locks.
--Access Privileges: SELECT on v$session, v$lock

SELECT sn.username, m.sid, m.type,
  DECODE(m.lmode, 0, 'None',
      1, 'Null',
      2, 'Row Share',
      3, 'Row Excl.',
      4, 'Share',
      5, 'S/Row Excl.',
      6, 'Exclusive',
    lmode, ltrim(to_char(lmode,'990'))) lmode,
  DECODE(m.request,0, 'None',
       1, 'Null',
       2, 'Row Share',
       3, 'Row Excl.',
       4, 'Share',
       5, 'S/Row Excl.',
       6, 'Exclusive',
       request, ltrim(to_char(m.request,
    '990'))) request, m.id1, m.id2
FROM v$session sn, v$lock m
WHERE (sn.sid = m.sid AND m.request != 0)
  OR (sn.sid = m.sid
    AND m.request = 0 AND lmode != 4
    AND (id1, id2) IN (SELECT s.id1, s.id2
  FROM v$lock s
      WHERE request != 0
    AND s.id1 = m.id1
        AND s.id2 = m.id2)
    )
ORDER BY id1, id2, m.request; 
robin@SZDB:~/dba_scripts/custom/sql> more request_lock_detail.sql
set linesize 190
col osuser format a15
col username format a20 wrap
col object_name format a20 wrap
col terminal format a25 wrap
col Req_Mode format a20
select B.SID, C.USERNAME, C.OSUSER, C.TERMINAL,
  DECODE(B.ID2, 0, A.OBJECT_NAME,
   'Trans-'||to_char(B.ID1)) OBJECT_NAME,
  B.TYPE,
  DECODE(B.LMODE,0,'--Waiting--',
      1,'Null',
      2,'Row Share',
      3,'Row Excl',
     4,'Share',
      5,'Sha Row Exc',
   6,'Exclusive',
      'Other') "Lock Mode",
  DECODE(B.REQUEST,0,' ',
      1,'Null',
      2,'Row Share',
      3,'Row Excl',
      4,'Share',
      5,'Sha Row Exc',
      6,'Exclusive',
      'Other') "Req_Mode"
 from DBA_OBJECTS A, V$LOCK B, V$SESSION C
where A.OBJECT_ID(+) = B.ID1
 and B.SID = C.SID
 and C.USERNAME is not null
order by B.SID, B.ID2;