轉自：http://www.itpub.net/thread-1703738-1-1.html
最近運行一個分批刪除數據的procedure，感覺運行比較慢，臨時取消了該job，然後再次重建procedure時，sessionhang住了，應該是library cache pin的等待事件了，oracle用兩種結構pin和lock來控制shared pool的併發訪問控制。
訪問一個對象將其pin到內存中，在pin之前需要先獲取該對象的handle的鎖定，lock的索引主要有nullshare exclusive，當然pin該對象也有上述三種狀態。
Session a ：execute delete_data
臨時取消了該procedure的運行，實際進程並沒有馬上釋放該對象的pin
Session b：
SQL> create orreplace procedure delete_data
2 as
3 begin
4 loop
Delete fromTEXTAUTO_FOLDERARTICLE where LASTPOSTDATE<sysdate-10 and rownum<10000;
Exit whensql%notfound;--dml語句中隱式遊標屬性進行控制
Commit;
End loop;
9 Commit;
10 end;
11 /
出現了library cache pin等待事件：
SQL> selectevent,count(*) from v$session group by event;
EVENT COUNT(*)
--------------------------------------------------------------------------
SQL*Net messagefrom client 92
library cachepin 1
jobq slavewait 1
rdbms ipcmessage 10
smon timer 1
pmon timer 1
db file scatteredread 1
Streams AQ: qmnslave idle wait 1
SQL*Net message toclient 1
Streams AQ: qmncoordinator idle wait 1
Streams AQ: waitingfor time management or cleanup tasks 1
11 rows selected.
分析一下上述的library cache pin是如何造成的：首先系統運行了該procedure，此時該對象已經被pin到內存，佔用了一個share pin和一個null lock，而此時在進程還沒有釋放此pin之前再次create procedure，此時要獲取一個exclusive pin和exclusivelock，由於之前的share pin和exclusivepin不共存，此時就會產生一個library cache pin等待。
這裏注意一下兩個基表x$kglpn和x$kgllk，對於解決library cache pin和lock太輕鬆了。
SQL> descx$kglpn;
Name Null? Type
------------------------------------------------- ----------------------------
ADDR RAW(8)
INDX NUMBER
INST_ID NUMBER
KGLPNADR RAW(8)
KGLPNUSE RAW(8)
KGLPNSES RAW(8)
KGLPNHDL RAW(8)
KGLPNLCK RAW(8)
KGLPNCNT NUMBER
KGLPNMOD NUMBER
KGLPNREQ NUMBER
KGLPNDMK NUMBER
KGLPNSPN NUMBER
通過等待事件的p1raw參數聯合kglpnhdl來獲取kglpnuse，這裏的kglpnmod和kglpnreq和v$lock的lmode和request基本相同，kglpnmod=2表示此時這個session佔有了library cache pin而造成了kglpnreq=3這個session的等待。
SQL> selectkglpnuse,kglpnhdl,kglpnmod,kglpnreq from x$kglpn where kglpnhdl in (selectp1raw from v$session where event='library cache pin');
KGLPNUSE KGLPNHDL KGLPNMOD KGLPNREQ
-------------------------------- ---------- ----------
00000000D822759000000000DD876D98 0 3
00000000DA22534000000000DD876D98 2 0
聯合v$session的saddr來獲取sid然後可以通過v$process來kill掉沒有釋放的進程。
SQL> selectb.spid,a.sid from v$session a,v$process b where a.saddr in ('00000000DA225340') and a.paddr=b.addr;
SPID SID
----------------------
11232 195
而如果此時再重新編譯一下該procedure，同樣需要獲取一個該對象的lock鎖定，由於上述重建procedure還在視圖獲取該對象的librarycache lock的exclusive lock，那麼當然此時出現librarycache lock是當然的。
SQL> alterprocedure delete_data compile;
SQL> selectevent,count(*) from v$session group by event;
EVENT COUNT(*)
--------------------------------------------------------------------------
SQL*Net messagefrom client 91
library cachepin 1
jobq slavewait 1
rdbms ipcmessage 10
smon timer 1
pmon timer 1
db file scatteredread 1
library cachelock 1
Streams AQ: qmnslave idle wait 1
SQL*Net message toclient 1
Streams AQ: qmncoordinator idle wait 1
SQL> descx$kgllk;
Name Null? Type
------------------------------------------------- ----------------------------
ADDR RAW(8)
INDX NUMBER
INST_ID NUMBER
KGLLKADR RAW(8)
KGLLKUSE RAW(8)
KGLLKSES RAW(8)
KGLLKSNM NUMBER
KGLLKHDL RAW(8)
KGLLKPNC RAW(8)
KGLLKPNS RAW(8)
KGLLKCNT NUMBER
KGLLKMOD NUMBER
KGLLKREQ NUMBER
KGLLKFLG NUMBER
KGLLKSPN NUMBER
KGLLKHTB RAW(8)
KGLNAHSH NUMBER
KGLLKSQLID VARCHAR2(13)
KGLHDPAR RAW(8)
KGLHDNSP NUMBER
USER_NAME VARCHAR2(30)
KGLNAOBJ VARCHAR2(60)
獲取blocking session的方法基本相同，也是通過p1raw參數聯合kgllkhdl來獲取kgllkuse，最後聯合v$session來獲取sid，進而通過v$process獲取spid，殺掉進程後即可
SQL> selectkgllkhdl,kgllkuse,kgllkreq,kgllkmod from x$kgllk where kgllkhdl in (Selectp1raw from v$session where event='library cache lock');
KGLLKHDL KGLLKUSE KGLLKREQ KGLLKMOD
-------------------------------- ---------- ----------
00000000DD876D9800000000DA225340 0 1
00000000DD876D9800000000D8227590 0 3
00000000DD876D9800000000D821FC40 3 0
通過上述的library cache pin和library cache lock等待事件的分析和診斷，可以看出數據字典基表可以提供我們非常的信息，而幫助解決一些比較棘手的案例，當然上述我們也可以利用oradebug然後通過trace文件來診斷，不過相對trace文件較難以閱讀，需要一定的功底，後續如果有對該等待事件trace的解決案例再拿出來與大家分享。
轉自：http://www.xifenfei.com/3172.html
library cache pin說明
library cache pin 事件是用來管理library cache的併發訪問的, pin一個object會引起相應的heap被載入內存中,如果客戶端需要修改或檢測這個object它就必須在鎖住後取得一個pin.library cache pin的等待時間爲3秒鐘,其中有1秒鐘用於PMON後臺進程,即在取得pin之前最多等待3秒鐘,否則就超時.library cache pin通常是發生在編譯或重新編譯PL/SQL,VIEW,TYPES等object時.編譯通常都是顯性的,如安裝應用程序,升級,安裝補丁程序等,但object的重新編譯也可能發生在object變得無效時.library
cache pin的參數如下,有用的主要是P1和P2:
P1 – KGL Handle address.
P2 – Pin address
P3 – 10*Mode + Namespace
其中,P1,P2可與x$kglpn和x$kglob表相關.x$kglpn和x$kglob是ORACLE數據庫的內部數據字典.
x$kglpn library cache pin信息
x$kglob library cache object信息
查詢方法一
--通過查詢V$SESSION_WAIT找出正在等待”library cache pin”的sessionSELECT
sid, SUBSTR (event, 1, 30), TO_CHAR(p1,
'xxxxxxxx') p1_16, --P1RAW P1_16, p2, p3 FROM
v$session_wait WHERE
wait_time = 0 AND
event LIKE 'library cache pin%';--P1 列是Library Cache Handle Address--P2 列是Library Cache Pin Address.
--找到相關session pin狀態SELECT
ADDR, INDX, KGLPNADR,-- Library Cache Pin Address KGLPNUSE, KGLPNSES,--識別鎖住此pin 的session KGLPNHDL,--Library Cache Handle Address kGLPNLCK, KGLPNMOD,-- Pin 鎖
KGLPNREQ-- Pin 請求 FROM
x$kglpn WHERE
KGLPNHDL LIKE
'%EB3EB8%';--p1_16 --詢X$KGLOB (Library Cache Object),可找到相關的objectSELECT
KGLNAOBJ-- 相關object的名字(取前面80個字符) FROM
X$KGLOB WHERE
KGLHDADR LIKE
'%EB3EB8%';--p1_16 --查出佔着pin鎖的session目前正在做什麼SELECT
a.sid, a.username, a.program FROM
v$session a, x$kglpn b WHERE
a.saddr = b.kglpnuse AND
b.kglpnhdl LIKE
'%EB3EB8%'--p1_16 AND
b.kgnmod <> 0; --查出阻塞者正執行的SQL語句 SELECT
sid, sql_text FROM
v$session, v$sqlarea WHERE
v$session.sql_address = v$sqlarea.address AND
sid =&sid; |
查詢方法二
--通過查詢DBA_LOCK_INTERNAL和V$SESSION_WAIT,可得到與”library cache pin” 等待相關的object的名字SELECT
TO_CHAR (SESSION_ID, '999') sid, SUBSTR (LOCK_TYPE, 1, 30) TYPE, SUBSTR (lock_id1, 1, 23) Object_Name, SUBSTR (mode_held, 1, 4) HELD, SUBSTR (mode_requested, 1, 4) REQ, lock_id2 Lock_addr FROM
dba_lock_internal WHERE
mode_requested <> 'None'
AND mode_requested <> mode_held AND
session_id IN (SELECT
sid FROM
v$session_wait WHERE
wait_time = 0 AND
event LIKE 'library cache pin%'); --查出”library cache pin”佔有者(即阻塞者)的session id SELECT
sid Holder, KGLPNUSE Sesion, KGLPNMOD Held, KGLPNREQ Req FROM
sys.x$kglpn, v$session WHERE
KGLPNHDL IN
(SELECT p1raw FROM
v$session_wait WHERE
wait_time = 0 AND
event LIKE 'library cache pin%') AND
KGLPNMOD <> 0 AND
v$session.saddr = x$kglpn.kglpnuse; --查出”library cache pin”佔有者(阻塞者)正在等什麼 SELECT
sid, SUBSTR (event, 1, 30), wait_time FROM
v$session_wait WHERE
sid IN (SELECT
sid FROM
x$kglpn, v$session WHERE
KGLPNHDL IN (SELECT
p1raw FROM
v$session_wait WHERE
wait_time = 0 AND
event LIKE
'library cache pin%') AND
KGLPNMOD <> 0 AND
v$session.saddr = x$kglpn.kglpnuse); --查出阻塞者正執行的SQL語句 SELECT
sid, sql_text FROM
v$session, v$sqlarea WHERE
v$session.sql_address = v$sqlarea.address AND
sid =&sid; |
