library cache pin和library cache lock(二)

在library cache pin和library cache lock(一)我們簡單介紹了介紹library cache pin和library cache lock的成因，下面介紹如何解決library cache pin和library cache lock等待。

三、解決方法

有兩種方法可以查詢library cache pin的相關資訊，推薦使用第二種。

使用這種方法前，有必要先了解以下表或檢視：x$kglob、x$kgllk、x$kglpn、DBA_KGLLOCK

1) x$kglob
該基表主要是library cache object的相關資訊。
X$KGLOB--[K]ernel [G]eneric [L]ibrary Cache Manager [OB]ject
引用該基表的檢視有﹕GV$ACCESS、GV$OBJECT_DEPENDENCY、GV$DB_OBJECT_CACHE、GV$DB_PIPES、DBA_LOCK_INTERNAL﹑DBA_DDL_LOCKS

2) x$kgllk
該基表儲存了library cache中物件的鎖資訊，主要用於解決library cache lock。
其名稱含義是：
[K]ernel Layer
[G]eneric Layer
[L]ibrary Cache Manager ( defined and mapped from kqlf )
Object Locks
X$KGLLK - Object [L]oc[K]s

引用該基表的檢視有﹕
DBA_DDL_LOCKS ﹑DBA_KGLLOCK ﹑GV$ACCESS ﹑GV$OPEN_CURSOR

SQL> desc x$kgllk;
名稱 型別
---------- -----------
ADDR RAW(4)
INDX NUMBER
INST_ID NUMBER
KGLLKADR RAW(4)
KGLLKUSE RAW(4) ---會話地址(對應v$session的saddr)
KGLLKSES RAW(4) ---owner地址
KGLLKSNM NUMBER ---SID
KGLLKHDL RAW(4) ---控制程式碼
KGLLKPNC RAW(4) ---the address of the call pin
KGLLKPNS RAW(4) ---對應跟蹤檔案中的session pin值
KGLLKCNT NUMBER
KGLLKMOD NUMBER ---持有鎖的模式(0為no lock/pin held﹐1為null,2為share﹐3為exclusive)
KGLLKREQ NUMBER ---請求鎖的模式(0為no lock/pin held﹐1為null,2為share﹐3為exclusive)
KGLLKFLG NUMBER ---cursor的狀態﹐8(10g前)或2048(10g)表示這個sql正在執行﹐
KGLLKSPN NUMBER ---對應跟蹤檔案的savepoint的值
KGLLKHTB RAW(4)
KGLNAHSH NUMBER ---sql的hash值(對應v$session的sql_hash_value)
KGLLKSQLID VARCHAR2(13) ---sql ID，sql識別符號
KGLHDPAR RAW(4) ---sql地址(對應v$session的sql_address)
KGLHDNSP NUMBER
USER_NAME VARCHAR2(30) ---會話的使用者名稱
KGLNAOBJ VARCHAR2(60) ---物件名稱或者已分析並開啟cursor的sql的前60個字元

3) x$kglpn
X$KGLPN--[K]ernel [G]eneric [L]ibrary Cache Manager object [P]i[N]s
它是與x$kgllk相對應的表﹐是關於pin的相關資訊。它主要用於解決library cache pin
引用該表的檢視有﹕
DBA_KGLLOCK

SQL> desc x$kglpn;
名稱 型別
------------ ----------------------------
ADDR RAW(4)
INDX NUMBER
INST_ID NUMBER
KGLPNADR RAW(4)
KGLPNUSE RAW(4) ---會話地址(對應v$session的saddr)
KGLPNSES RAW(4) ---owner地址
KGLPNHDL RAW(4) ---控制程式碼
KGLPNLCK RAW(4)
KGLPNCNT NUMBER
KGLPNMOD NUMBER ---持有pin的模式(0為no lock/pin held﹐1為null,2為share﹐3為exclusive)
KGLPNREQ NUMBER ---請求pin的模式(0為no lock/pin held﹐1為null,2為share﹐3為exclusive)
KGLPNDMK NUMBER
KGLPNSPN NUMBER ---對應跟蹤檔案的savepoint的值

4) DBA_KGLLOCK
DBA_KGLLOCK是一個檢視，它聯合了x$kgllk和x$kglpn的部分資訊。
透過查詢，我們可以知道DBA_KGLLOCK檢視的構建語句：
SQL> SELECT * FROM DBA_VIEWS WHERE VIEW_NAME='DBA_KGLLOCK';

select kgllkuse, kgllkhdl, kgllkmod, kgllkreq, 'Lock' kgllktype from x$kgllk
union all
select kglpnuse, kglpnhdl, kglpnmod, kglpnreq, 'Pin' kgllktype from x$kglpn


瞭解了用到的幾個主要檢視或表的結構，我們就可以寫出編寫查詢來檢視相關資訊：

方法一、只能查詢library cache pin相關資訊

SQL> SELECT distinct decode(kglpnreq,0,'holding_session: '||s.sid,'waiting_session: '||s.sid) sid,
2 s.SERIAL#, kglpnmod "Pin Mode", kglpnreq "Req Pin",a.sql_text,kglnaown "Owner", kglnaobj "Object"
3 FROM x$kglpn p, v$session s,v$sqlarea a,v$session_wait sw,x$kglob x
4 WHERE p.kglpnuse=s.saddr
5 AND kglpnhdl=sw.p1raw
6 and kglhdadr=sw.p1raw
7 and event like 'library cache%'
8 and (a.hash_value, a.address) IN (
9 select
10 DECODE (sql_hash_value,
11 0,
12 prev_hash_value,
13 sql_hash_value
14 ),
15 DECODE (sql_hash_value, 0, prev_sql_addr, sql_address)
16 from v$session s2
17 where s2.sid=s.sid
18 )
19 ;

SID SERIAL# Pin Mode Req Pin SQL_TEXT Owner Object
-------------------- ---------- ---------- ---------- ---------------------------------------- ------------ --------------------
blocked_sid: 16 195 0 3 grant execute on p_s SUK P_SLEEP
blocker_sid: 20 15 2 0 begin p_sleep; end; SUK P_SLEEP

得到這個結果後，你可以根據實際情況kill掉阻塞的會話或者被阻塞的會話。

方法二、可以查詢library cache pin和library cache lock 的資訊

select Distinct /*+ ordered */ w1.sid waiting_session,
h1.sid holding_session,
w.kgllktype lock_or_pin,
od.to_owner object_owner,
od.to_name object_name,
oc.Type,
decode(h.kgllkmod, 0, 'None', 1, 'Null', 2, 'Share', 3, 'Exclusive',
'Unknown') mode_held,
decode(w.kgllkreq, 0, 'None', 1, 'Null', 2, 'Share', 3, 'Exclusive',
'Unknown') mode_requested,
xw.KGLNAOBJ wait_sql,xh.KGLNAOBJ hold_sql
from dba_kgllock w, dba_kgllock h, v$session w1,
v$session h1,v$object_dependency od,V$DB_OBJECT_CACHE oc,x$kgllk xw,x$kgllk xh
where
(((h.kgllkmod != 0) and (h.kgllkmod != 1)
and ((h.kgllkreq = 0) or (h.kgllkreq = 1)))
and
(((w.kgllkmod = 0) or (w.kgllkmod= 1))
and ((w.kgllkreq != 0) and (w.kgllkreq != 1))))
and w.kgllktype = h.kgllktype
and w.kgllkhdl = h.kgllkhdl
and w.kgllkuse = w1.saddr
and h.kgllkuse = h1.saddr
And od.to_address = w.kgllkhdl
And od.to_name=oc.Name
And od.to_owner=oc.owner
And w1.sid=xw.KGLLKSNM
And h1.sid=xh.KGLLKSNM
And (w1.SQL_ADDRESS=xw.KGLHDPAR And w1.SQL_HASH_VALUE=xw.KGLNAHSH)
And (h1.SQL_ADDRESS=xh.KGLHDPAR And h1.SQL_HASH_VALUE=xh.KGLNAHSH)
;

WAITING_SESSION HOLDING_SESSION LOCK_OR_PIN OBJECT_OWNER OBJECT_NAME TYPE MODE_HELD MODE_REQUESTED WAIT_SQL HOLD_SQL
--------------- --------------- ----------- ---------------------------------------------------------------- -------------------------------------------------------------------------------- ---------------------------- --------- -------------- ------------------------------------------------------------ ------------------------------------------------------------
18 19 Lock SUK P_SLEEP PROCEDURE Exclusive Exclusive grant execute on p_sleep to system grant execute on p_sleep to system
19 12 Pin SUK P_SLEEP PROCEDURE Share Exclusive grant execute on p_sleep to system begin p_sleep; end;
23 25 Lock SUK P_SLEEP2 PROCEDURE Exclusive Exclusive grant execute on p_sleep2 to system grant execute on p_sleep2 to system
25 14 Pin SUK P_SLEEP2 PROCEDURE Share Exclusive grant execute on p_sleep2 to system begin p_sleep2; end;


為了避免這種情況，可以在編譯過程或函式等物件時，先檢視一下是否有會話正在使用該物件，查詢語句如下：

SELECT Distinct sid using_sid,
s.SERIAL#, kglpnmod "Pin Mode", kglpnreq "Req Pin",kglnaown "Owner", kglnaobj "using_Object"
FROM x$kglpn p, v$session s,x$kglob x
WHERE p.kglpnuse=s.saddr
AND kglpnhdl=kglhdadr
And p.KGLPNUSE = s.saddr
And kglpnreq=0
And upper(kglnaobj) = upper('&obj');

如果有結果返回，則等待這些對話的操作執行完畢再重新編譯，也可以把這些會話kill。

四、其他解決方法
上面主要是用到SQL查詢相關資訊的解決方法，也可以使用10046、trace等方法實現。至於用那種方法好，見仁見智。