检查oracle 数据阻塞,Oracle阻塞(blockingblocked)实例详解

一时失言乱红尘 2022-10-21 01:25 550阅读 0赞

一、概述：

阻塞是DBA经常碰到的情形，尤其是不良的应用程序设计所造成的阻塞将导致数据库性能的严重下降，直至数据库崩溃。对DBA而言，有必要知道如何定位到当前系统有哪些阻塞，到底谁是阻塞者，谁是被阻塞者。本文对此给出了描述并做了相关演示。

二、演示阻塞：

\--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

三、文中涉及到的相关SQL脚本完整代码如下：

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;

检查oracle 数据阻塞,Oracle阻塞(blockingblocked)实例详解

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