Oracle单实例情况下的library cache pin的问题模拟与问题分析

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本文通过创建多个用户及对象，在Oracle单实例环境下模拟了library cache pin等待事件的发生，并详细分析了如何定位引发该等待事件的对象及锁定双方。

Oracle单实例情况下的library cache pin的问题模拟与问题分析

参考自：

WAITEVENT: "library cache pin" Reference Note (文档 ID 34579.1)
How to Find the Blocker of the 'library cache pin' in a RAC environment? (文档 ID 780514.1)

本机环境：Oracle 10.2.0.5 x86-64bit for RHEL5.8 x86-64bit

第一个session：

[oracle@localhost ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Fri Jun 12 17:27:28 2015

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area  281018368 bytes
Fixed Size                  2095672 bytes
Variable Size              96470472 bytes
Database Buffers          176160768 bytes
Redo Buffers                6291456 bytes
Database mounted.
Database opened.

SQL> create user lc0019999 identified by aaaaaa;

User created.

SQL> grant dba to lc0019999;

Grant succeeded.

SQL> create user lc0029999 identified by aaaaaa;

User created.

SQL> grant dba to lc0029999;

Grant succeeded.

SQL> create user lc0039999 identified by aaaaaa;

User created.

SQL> grant dba to lc0039999;

Grant succeeded.

SQL> conn lc0019999/aaaaaa
Connected.
SQL> show user
USER is "LC0019999"

SQL> select * from v$mystat where rownum<2;

       SID STATISTIC#      VALUE
---------- ---------- ----------
       159          0          1

SQL> Create or replace procedure dummy is
  2   begin
  3   null;
  4   end;
  5   /

Procedure created.


SQL> Begin
  2   Dummy;
  3   Dbms_lock.sleep(1000);
  4   End;
  5   /
------------>一直sleep着

以lc0029999登陆新开的一个session

[oracle@localhost ~]$ sqlplus lc0029999/aaaaaa

SQL*Plus: Release 10.2.0.5.0 - Production on Fri Jun 12 17:34:04 2015

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select * from v$mystat where rownum<2;

       SID STATISTIC#      VALUE
---------- ---------- ----------
       158          0          1

SQL> 
SQL> alter procedure lc0019999.dummy compile;

------------>一直hang着

以sys用户新开一个session

[oracle@localhost ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Fri Jun 12 17:31:33 2015

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> set line 200
SQL> select sid, serial#,event from v$session where event like '%library cache pin%';

       SID    SERIAL# EVENT
---------- ---------- ----------------------------------------------------------------
       158         28 library cache pin

SQL> select sid, serial#,p1raw,event from v$session where event like '%library cache pin%';

       SID    SERIAL# P1RAW            EVENT
---------- ---------- ---------------- --------------------------------------------------
       158         28 000000006BFF19B0 library cache pin

SQL> col owner for a30
SQL> col object for a30
SQL> SELECT kglnaown "Owner", kglnaobj "Object"
  2  FROM x$kglob
  3  WHERE kglhdadr='000000006BFF19B0'---->上面查出的P1RAW值。
  4  ;                                ---->该语句是查询出这个等待事件发生在哪个object上。

Owner                          Object
------------------------------ ------------------------------
LC0019999                      DUMMY

SQL> 
SQL> SELECT s.sid, kglpnmod "Mode", kglpnreq "Req"
  2      FROM x$kglpn p, v$session s
  3     WHERE p.kglpnuse=s.saddr
  4       AND kglpnhdl='000000006BFF19B0';---->该语句是查询出这个等待事件的等待者sid（REQ>0）和持有者sid（Mode>0）

       SID       Mode        Req
---------- ---------- ----------
       158          0          3
       159          2          0

SQL> 
---补充：如下文字来源于：
<blockquote><strong><code>Mode</code></strong><span> </span>is the mode in which the pin is wanted. This is a number thus:<ul><li>2 - Share mode</li><li>3 - Exclusive mode</li></ul></blockquote>

 
如下摘自：WAITEVENT: "library cache pin" Reference Note (文档 ID 34579.1)
 An X request (3) will be blocked by any pins held S mode (2) on the object.
 An S request (2) will be blocked by any X mode (3) pin held, or may queue behind some other X request.