问题描述：接到应用人员的报告，说是在任何对表CSNOZ629926699966的操作都会hang，包括desc CSNOZ629926699966,例如：
> sqlplus
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Jan 10 10:11:06 2005
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
SQL> conn pubuser/pubuser
Connected.
SQL> desc CSNOZ629926699966
。。。
这个进程hang了
。。。
询问了一下之前有无特别的操作，业务人员说很久以前执行了脚本，但是该教本运行很久都没有结果，然后他就退出了会话，再之后，就出现了上面的情况。脚本内容如下：$ cat CSNOZ629926699966.sh
#!/bin/sh
sqlplus << EOF #use your username/password
create table CSNOZ629926699966 as select * from CSNOZ62992266cs
where mid not in ( select mid from where servid='020999011964' and status in ('A','B','S'));
exit;
$
$
$
$
解决过程：> sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Jan 10 10:19:13 2005
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
SQL> select * from v$lock where block=1;
no rows selected
SQL> /
no rows selected
SQL> /
no rows selected
SQL>我们看到目前没有锁的信息
SQL> select xidusn, object_id, session_id, locked_mode from v$locked_object;
。。。
XIDUSN OBJECT_ID SESSION_ID LOCKED_MODE
---------- ---------- ---------- -----------
14 18 37 3
。。。
SQL> /
。。。
XIDUSN OBJECT_ID SESSION_ID LOCKED_MODE
---------- ---------- ---------- -----------
14 18 37 3
。。。
SQL> /
。。。
XIDUSN OBJECT_ID SESSION_ID LOCKED_MODE
---------- ---------- ---------- -----------
14 18 37 3
。。。
SQL>查找v$locked_object，我们发现了一个可疑的会话，SID 37：
SQL> select object_name,owner,object_type from dba_objects where object_id=18;
。。。 。。。
OBJECT_NAME OWNER OBJECT_TYPE
------------------------------ ------------------------------ ------------------
OBJ$ SYS TABLE
。。。 。。。
SQL>
奇怪怎么一直有这个锁？？初步猜测是由于SID为37的会话执行了上面的DDL语句，并在语句未完成前异常退出，造成了所有访问那个(DDL语句中涉及到的)对象的进程都hang了。
接下来我们看看等待事件：SQL> select event,sid,p1,p2,p3 from v$session_wait where event not like 'SQL*%' and event not like 'rdbms%';
EVENT P1 P2 SID
---------------------------------------------------------------- ---------- ---------- ----------
pmon timer 300 0 1
ges remote message 32 0 4
gcs remote message 64 0 5
gcs remote message 64 0 7
smon timer 300 0 19
library cache lock 1.3835E+19 1.3835E+19 30wakeup time manager 0 0 22
7 rows selected.
SQL> /
EVENT P1 P2 SID
---------------------------------------------------------------- ---------- ---------- ----------
pmon timer 300 0 1
ges remote message 32 0 4
gcs remote message 64 0 5
gcs remote message 64 0 7
smon timer 300 0 19
library cache lock 1.3835E+19 1.3835E+19 30wakeup time manager 0 0 22
7 rows selected.
SQL> /
EVENT P1 P2 SID
---------------------------------------------------------------- ---------- ---------- ----------
pmon timer 300 0 1
ges remote message 32 0 4
gcs remote message 64 0 5
gcs remote message 64 0 7
smon timer 300 0 19
library cache lock 1.3835E+19 1.3835E+19 30wakeup time manager 0 0 22
7 rows selected.
SQL> /
EVENT P1 P2 SID
---------------------------------------------------------------- ---------- ---------- ----------
pmon timer 300 0 1
ges remote message 32 0 4
gcs remote message 64 0 5
gcs remote message 64 0 7
smon timer 300 0 19
library cache lock 1.3835E+19 1.3835E+19 30wakeup time manager 0 0 22
7 rows selected.
SQL>
我们注意到下面的事件：EVENT P1 P2 SID
---------------------------------------------------------------- ---------- ---------- ----------。。。
library cache lock 1.3835E+19 1.3835E+19 30
。。。
P1是句柄地址(handle address),也就是'library cache lock'发生的地址。P2是一个状态对象，在这里，它表示在对象上加载的锁的地址(lock address)。P1和P2都是科学计数发表示的10进制数。
这些信息再次证实了上面的猜测，SID 37阻塞了SID 30。
找出这两个可疑进程的sid和serial，然后对他们设置10046事件：SQL> select sid,serial# from v$session where sid in (30,37);
SID SERIAL#
---------- ----------
30 24167
37 2707
SQL> exec dbms_system.set_ev(30,24167,10046,12,'');
PL/SQL procedure successfully completed.
SQL> exec dbms_system.set_ev(37,2707,10046,12,'');
PL/SQL procedure successfully completed.
SQL>
跟踪期间咱们再次测试一下，看看有没有其他线索。
新开一个进程，找出其sid, serial和spid等信息：> sqlplus pubuser/pubuser
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Jan 10 11:36:25 2005
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
SQL> select distinct sid from v$mystat;
SID
----------
33
SQL> select sid,serial# from v$session where sid=33;
SID SERIAL#
---------- ----------
33 6639
SQL> SELECT SPID,PID FROM V$PROCESS WHERE ADDR=(SELECT PADDR FROM V$SESSION WHERE SID=37);
SPID PID
------------ ----------
20552 26
SQL> SELECT SPID,PID FROM V$PROCESS WHERE ADDR=(SELECT PADDR FROM V$SESSION WHERE SID=30);
SPID PID
------------ ----------
22580 28
SQL> show parameter dump
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
background_core_dump string partial
background_dump_dest string /ora9i/app/oracle/admin/csmisc
/bdump
core_dump_dest string /ora9i/app/oracle/admin/csmisc
/cdump
max_dump_file_size string UNLIMITED
shadow_core_dump string partial
user_dump_dest string /ora9i/app/oracle/admin/csmisc
/udump
SQL>
然后，再尝试对CSNOZ629926699966表进行操作SQL> desc CSNOZ629926699966
。。。
还是hang住了。
于是中断这个操作(CTRL + C)：
SQL> desc CSNOZ629926699966
ERROR:
ORA-01013: user requested cancel of current operation
SQL> select tname from tab where tname='CSNOZ629926699966';
no rows selected
SQL>查看PUBUSER用户下的这个表，居然不存在！！
进一步证实了前面的猜测，也就是说会话37阻塞了其他所有操作表CSNOZ629926699966的会话，造成了进程的hang，当然，包括上面的SID 30和SID 33的DDL语句
现在，我们结束10046的事件跟踪：SQL> exec dbms_system.set_ev(30,24167,0,0,'');
PL/SQL procedure successfully completed.
SQL> exec dbms_system.set_ev(37,2707,0,0,'');
PL/SQL procedure successfully completed.
SQL>
根据上面记录的信息，我们知道这两个会话产生的跟踪信息分别为：SID为30的会话，产生的跟踪文件为：/ora9i/app/oracle/admin/csmisc/udump/csmisc2_ora_22580.trc
SID为37的会话，产生的跟踪文件为：/ora9i/app/oracle/admin/csmisc/udump/csmisc2_ora_20552.trc
看看trace文件：> cd /ora9i/app/oracle/admin/csmisc/udump
> ll -tlc
total 4432
-rw-r----- 1 ora9i dba 332995 Jan 10 12:00 csmisc2_ora_22580.trc
-rw-r----- 1 ora9i dba 3168 Jan 10 11:59 csmisc2_ora_20552.trc-rw-r----- 1 ora9i dba 407133 Jan 7 15:10 csmisc2_ora_2708.trc
-rw-r----- 1 ora9i dba 640 Jan 7 14:48 csmisc2_ora_835.trc
-rw-r----- 1 ora9i dba 1590 Dec 30 22:50 csmisc2_ora_16244.trc
-rw-r----- 1 ora9i dba 1308403 Dec 30 22:44 csmisc2_ora_16033.trc
-rw-r----- 1 ora9i dba 616 Dec 28 14:16 csmisc2_ora_2176.trc
-rw-r----- 1 ora9i dba 644 Dec 8 18:22 csmisc2_ora_21083.trc
> mailx -s "csmisc2_ora_22580.trc" < csmisc2_ora_22580.trc
> mailx -s "csmisc2_ora_20552.trc" < csmisc2_ora_20552.trc
> exit
SQL>
我们看到SID为30的会话，产生的跟踪文件(csmisc2_ora_22580.trc)为的主要内容是：/ora9i/app/oracle/admin/csmisc/udump/csmisc2_ora_22580.trc
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
ORACLE_HOME = /ora9i/app/oracle/product/920
System name: HP-UX
Node name: cs_dc02
Release: B.11.11
Version: U
Machine: 9000/800
Instance name: csmisc2Redo thread mounted by this instance: 2
Oracle process number: 28
Unix process pid: 22580, image: (TNS V1-V3)
*** 2005-01-10 11:31:49.416
*** SESSION ID:(30.24167) 2005-01-10 11:31:49.354
WAIT #0: nam='library cache lock' ela= 507258 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 505686 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507678 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507595 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507880 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507317 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507703 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507683 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 508265 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507100 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507684 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 505889 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507731 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507650 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507604 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
WAIT #0: nam='library cache lock' ela= 507698 p1=-4611686013547141416 p2=-4611686013691716064 p3=1301
。。。 。。。
我们看到SID 30的跟踪文件中的等待事件就是在V$SESSION_WAIT中看到的'library cache lock' .
再看看SID为37的会话，产生的跟踪文件(csmisc2_ora_20552.trc)为的主要内容是：Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
ORACLE_HOME = /ora9i/app/oracle/product/920
System name: HP-UX
Node name: cs_dc02Release: B.11.11
Version: U
Machine: 9000/800
Instance name: csmisc2Redo thread mounted by this instance: 2
Oracle process number: 26
Unix process pid: 20552, image: (TNS V1-V3)
*** 2005-01-10 11:33:22.702
*** SESSION ID:(37.2707) 2005-01-10 11:33:22.690
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
*** 2005-01-10 11:35:07.452
WAIT #1: nam='SQL*Net message from dblink' ela= 102293555 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 3 p1=675562835 p2=1 p3=0*** 2005-01-10 11:36:55.980
WAIT #1: nam='SQL*Net message from dblink' ela= 105969709 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
*** 2005-01-10 11:39:05.416
WAIT #1: nam='SQL*Net message from dblink' ela= 126390826 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
*** 2005-01-10 11:41:12.878
WAIT #1: nam='SQL*Net message from dblink' ela= 124461520 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
*** 2005-01-10 11:43:01.285
WAIT #1: nam='SQL*Net message from dblink' ela= 105859385 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
*** 2005-01-10 11:44:48.200
WAIT #1: nam='SQL*Net message from dblink' ela= 104397696 p1=675562835 p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835 p2=1 p3=0
。。。 。。。
现在我们来dump系统状态(systemstate)，看看更详细的信息。
首先简单的介绍一下event systemstate。很多人把systemstate事件理解为dump发生的那一刻的系统内所有进程的信息，这是个错误的概念，事实上，转储system state产生的跟踪文件是从dump那一刻开始到dump任务完成之间一段事件内的系统内所有进程的信息。
dump systemstate产生的跟踪文件包含了系统中所有进程的进程状态等信息。每个进程对应跟踪文件中的一段内容，反映该进程的状态信息，包括进程信息，会话信息，enqueues信息(主要是lock的信息)，缓冲区的信息和该进程在SGA区中持有的(held)对象的状态等信息。
那么通常在什么情况下使用systemstate比较合适呢？Oracle推荐的使用systemstate事件的几种情况是：
数据库hang住了
数据库很慢
进程正在hang
数据库出现某些错误
资源争用
dump systemstate的语法为：ALTER SESSION SET EVENTS 'immediate trace name systemstate level 10';
也可以使用ORADEBUG实现这个功能ORADEBUG DUMP SYSTEMSTATE level 10
如果希望在数据库发生某种错误时除非systemstate事件，可以在参数文件(spfile或者pfile)中设置event参数，例如，当系统发生死锁(出现ORA-00060错误)时dump systemstate：event = "60 trace name systemstate level 10"
言归正传，我们dump系统状态：SQL> ALTER SESSION SET EVENTS 'IMMEDIATE TRACE NAME SYSTEMSTATE LEVEL 8';
Session altered.
SQL> host
>cd /ora9i/app/oracle/admin/csmisc/udump
> ll -ctl
-rw-r----- 1 ora9i dba 1070863 Jan 10 13:02 csmisc2_ora_22580.trc
-rw-r----- 1 ora9i dba 1345368 Jan 10 13:01 csmisc2_ora_22568.trc-rwxrwxrwx 1 ora9i dba 44114 Jan 10 12:52 ass1015.awk
-rw-r----- 1 ora9i dba 407133 Jan 7 15:10 csmisc2_ora_2708.trc
-rw-r----- 1 ora9i dba 640 Jan 7 14:48 csmisc2_ora_835.trc
-rw-r----- 1 ora9i dba 1590 Dec 30 22:50 csmisc2_ora_16244.trc
-rw-r----- 1 ora9i dba 1308403 Dec 30 22:44 csmisc2_ora_16033.trc
-rw-r----- 1 ora9i dba 616 Dec 28 14:16 csmisc2_ora_2176.trc
-rw-r----- 1 ora9i dba 644 Dec 8 18:22 csmisc2_ora_21083.trc
>
> mailx -s "22568" < csmisc2_ora_22568.trc
这个跟踪文件很大(因为它包含了所有进程的信息)，那么我们从哪里开始看起呢？
首先，通过在跟踪文件中查找字符串"waiting for 'library cache lock'"，我们找到了被阻塞进程的信息：
PROCESS 28: ----------------被阻塞的Oracle进程，这里PROCESS 28对应了V$PROCESS中的PID的值，也就是说我们可以根据这一信息在V$PROCESS和V$SESSION找到被阻塞的会话的信息----------------------------------------
SO: c000000109c83bf0, type: 2, owner: 0000000000000000, flag: INIT/-/-/0x00
(process) Oracle pid=28, calls cur/top: c00000010b277890/c00000010b277890, flag: (0) -
int error: 0, call error: 0, sess error: 0, txn error 0
(post info) last post received: 17 24 6
last post received-location: ksusig
last process to post me: c000000109c840f8 25 0
last post sent: 0 0 15
last post sent-location: ksasnd
last process posted by me: c000000109c7ff90 1 6
(latch info) wait_event=0 bits=0
Process Group: DEFAULT, pseudo proc: c000000109eefda0
O/S info: user: ora9i, term: pts/th, ospid: 22580 ----------------该进程的操作系统进程号，对应于V$PROCESS中的SPIDOSD pid info: Unix process pid: 22580, image: (TNS V1-V3)
----------------------------------------
SO: c000000109f02c68, type: 4, owner: c000000109c83bf0, flag: INIT/-/-/0x00
(session) trans: 0000000000000000, creator: c000000109c83bf0, flag: (100041) USR/- BSY/-/-/-/-/-
DID: 0002-001C-00000192, short-term DID: 0000-0000-00000000
txn branch: 0000000000000000
oct: 0, prv: 0, sql: c00000011f8ea068, psql: c00000011f8ea068, user: 50/PUBUSER
O/S info: user: ora9i, term: , ospid: 22536, machine: cs_dc02
program:(TNS V1-V3)
application name: SQL*Plus, hashvalue=3669949024waiting for 'library cache lock' blocking sess=0x0seq=18589 wait_time=0handle address=c000000122e2a6d8, lock address=c00000011a449e20, 100*mode+namespace=515
。。。 。。。
SO: c00000010b277890, type: 3, owner: c000000109c83bf0, flag: INIT/-/-/0x00
(call) sess: cur c000000109f02c68, rec 0, usr c000000109f02c68; depth: 0
----------------------------------------
SO: c00000011a449e20, type: 51, owner: c00000010b277890, flag: INIT/-/-/0x00
LIBRARY OBJECT LOCK: lock=c00000011a449e20 handle=c000000122e2a6d8 request=S
call pin=0000000000000000 session pin=0000000000000000
htl=c00000011a449e90[c00000011a4bc350,c00000011a4bc350] htb=c00000011a4bc350
user=c000000109f02c68 session=c000000109f02c68 count=0 flags=[00] savepoint=463
the rest of the object was already dumped
。。。 。。。
请注意下面的信息：waiting for 'library cache lock' blocking sess=0x0 seq=18589 wait_time=0
handle address=c000000122e2a6d8, lock address=c00000011a449e20, 100*mode+namespace=515
这段信息告诉我们ORACLE PID为28的进程(PROCESS 28)，正在等待'library cache lock'，通过‘handle address=c000000122e2a6d8’我们可以找到阻塞它的会话的ORACLE PID信息。
还要注意这段信息：LIBRARY OBJECT LOCK: lock=c00000011a449e20 handle=c000000122e2a6d8 request=S
call pin=0000000000000000 session pin=0000000000000000
htl=c00000011a449e90[c00000011a4bc350,c00000011a4bc350] htb=c00000011a4bc350
user=c000000109f02c68 session=c000000109f02c68 count=0 flags=[00] savepoint=463
这里就是阻塞PROCESS 28进程的会话的信息。
简单的记住这个依据的要点是：
waiting session的'handle address'的值对应于blocking session的'handle'的值。
回过头来，看看这个值，它应于上面我们在V$SESSION_WAIT中看到的P1和P2的值：SQL> select to_number('C000000122E2A6D8','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX') from dual;
TO_NUMBER('C000000122E2A6D8','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
----------------------------------------------------------------
1.3835E+19
SQL>
问题的成因已经基本上明确了，这里推荐两种解决问题的方法：方法1，根据c000000122e2a6d8地址，我们可以得到当前在library cache中相应的锁信息：SQL> l
1 select INST_ID,USER_NAME,KGLNAOBJ,KGLLKSNM,KGLLKUSE,KGLLKSES,KGLLKMOD,KGLLKREQ,KGLLKPNS,KGLLKHDL
2* from X$KGLLK where KGLLKHDL = 'C000000122E2A6D8' order by KGLLKSNM,KGLNAOBJ
SQL> /
INST_ID USER_NAME KGLNAOBJ KGLLKSNM KGLLKUSE KGLLKSES KGLLKMOD KGLLKREQ KGLLKPNS KGLLKHDL
---------- ------------- ---------------------- ---------- ---------------- ---------------- ---------- ---------- ---------------- ----------------
2 PUBUSER CSNOZ629926699966 30 C000000109F02C68 C000000109F02C680 2 00 C000000122E2A6D8
2 PUBUSER CSNOZ629926699966 37 C000000108C99E28 C000000108C99E283 0 00 C000000122E2A6D8
SQL>
按照Oracle推荐的做法，我们现在应该使用'alter system kill session'命令kill掉SID 37，结果得到了ORA-00031错误：SQL> alter system kill session '37,2707';
alter system kill session '37,2707'
*
ERROR at line 1:
ORA-00031: session marked for kill
SQL>
检查SID 37的状态：SQL> set linesize 150
SQL> col program for a50
SQL> select sid,serial#,status,username,program from v$session where sid=37;
SID SERIAL# STATUS USERNAME PROGRAM
---------- ---------- -------- ------------------------------ --------------------------------------------------
37 2707 KILLED PUBUSER (TNS V1-V3)
SQL>再次证实了我们最初的想法——有人在执行了某个需要运行很久的DDL(多数是语句效率低，当然不排除遭遇bug的可能)，然后没等语句结束就异常退出了会话。
这个例子中我们在上面的跟踪文件已经找到了该会话对应的操作系统进程(SPID)，如果在其他情况下，我们如何找到这种状态为'KILLED'的操作系统进程号(SPID)呢？下面给出了一个方法，可以借鉴：SQL> l
1 SELECT s.username,s.status,
2 x.ADDR,x.KSLLAPSC,x.KSLLAPSN,x.KSLLASPO,x.KSLLID1R,x.KSLLRTYP,
3 decode(bitand (x.ksuprflg,2),0,null,1)
4 FROM x$ksupr x,v$session s
5 WHERE s.paddr(+)=x.addr
6 and bitand(ksspaflg,1)!=0
7* and s.sid=37
SQL> /
USERNAME STATUS ADDR KSLLAPSC KSLLAPSN KSLLASPO KSLLID1R KS D
------------------------------ -------- ---------------- ---------- ---------- ------------ ---------- -- -
PUBUSER KILLED C000000109C831E0 41 15 16243 17
SQL>
x$ksupr.ADDR列的值对应了V$PROCESS中的ADDR的值，知道了这个SPID的地址，找到这个操作系统进程(SPID)就简单了，例如：SQL> select spid,pid from v$process where addr='C000000109C831E0';
SPID PID
------------ ----------
20552 26
SQL>
现在，我们只需要在操作系统上kill操作系统进程20552就可以了：> ps -ef | grep 20552
ora9i 20552 1 0 Jan 8 ? 0:01 oraclecsmisc2 (LOCAL=NO)
ora9i 14742 14740 0 17:19:02 pts/ti 0:00 grep 20552
> kill -9 20552
> ps -ef | grep 20552
ora9i 14966 14964 0 17:40:01 pts/ti 0:00 grep 20552
>
再来检查一下SID 37的信息，我们看到这个会话是真的被kill掉了，> exit
SQL> select sid,serial#,status,username,program from v$session where sid=37;
no rows selected
SQL> l
1 SELECT s.username,s.status,
2 x.ADDR,x.KSLLAPSC,x.KSLLAPSN,x.KSLLASPO,x.KSLLID1R,x.KSLLRTYP,
3 decode(bitand (x.ksuprflg,2),0,null,1)
4 FROM x$ksupr x,v$session s
5 WHERE s.paddr(+)=x.addr
6 and bitand(ksspaflg,1)!=0
7* and s.sid=37
SQL> /
no rows selected
SQL>
回到刚才hang住的会话，它已经恢复了正常操作，并且我们已经得到了'ORA-04043: object CSNOZ629926699966 does not exist'这个正常的信息：SQL> desc CSNOZ629926699966
ERROR:
ORA-04043: object CSNOZ629926699966 does not exist
SQL>
在开一个会话，测试一把:
> sqlplus pubuser/pubuser
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Jan 10 17:42:16 2005
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning and Real Application Clusters options
JServer Release 9.2.0.4.0 - Production
SQL> set timing on
SQL> desc CSNOZ629926699966
ERROR:
ORA-04043: object CSNOZ629926699966 does not exist
SQL>当发出命令'desc CSNOZ629926699966'的时候，我们看到系统立刻返回了ORA-04043: object CSNOZ629926699966 does not exist'信息，问题就此解决了。
这里，简单的介绍一下X$KGLLK，这个基表保存了库缓存中对象的锁的信息，它对于解决这类问题特别有用，其名称的含义如下：[K]ernel Layer
[G]eneric Layer
[L]ibrary Cache Manager ( defined and mapped from kqlf )
Object Locks
X$KGLLK - Object [L]oc[K]s
KGLNAOBJ列包含了在librarky cache中的对象上执行命令的语句的前80个字符(其实从这里我们也可以大大缩小范围了)X$KGLLK.KGLLKUSE和x$kgllk.KGLLKSES对应于跟踪文件中的owner的值X$KGLLK.KGLLKADR
X$KGLLK.KGLLKHDL对应于跟踪文件中的handle的值(handle=C000000122E2A6D8)，也就是'library cache lock'的地址X$KGLLK.KGLLKPNS对应于跟踪文件中的session pin的值X$KGLLK.KGLLKSPN对应于跟踪文件中的savepoint的值
我们再来看一下更全面的信息：SQL> set linesize 2000
SQL> select * from X$KGLLK where KGLLKHDL = 'C000000122E2A6D8' order by KGLLKSNM,KGLNAOBJ
2 /
ADDR INDX INST_ID KGLLKADR KGLLKUSE KGLLKSES KGLLKSNM KGLLKHDL KGLLKPNC KGLLKPNS KGLLKCNT KGLLKMOD KGLLKREQ KGLLKFLG KGLLKSPN KGLLKHTB KGLNAHSH KGLHDPAR KGLHDNSP USER_NAME KGLNAOBJ
---------------- ---------- ---------- ---------------- ---------------- ---------------- ---------- ---------------- ---------------- ---------------- ---------- ---------- ---------- ---------- ---------- ---------------- ---------- ---------------- ---------- ------------------------------ ------------------------------------------------------------
800003FB0007E4D0 33 2 C00000011A449E20 C000000109F02C68 C000000109F02C68 30 C000000122E2A6D8 00 00 0 0 2 0 463 C00000011A4BC350 3990848181 C000000122E2A6D8 1 PUBUSER CSNOZ629926699966
800003FB0007E5B0 34 2 C00000011A44A150 C000000108C99E28 C000000108C99E28 37 C000000122E2A6D8 00 00 1 3 0 0 179 C00000011A4BB328 3990848181 C000000122E2A6D8 1 PUBUSER CSNOZ629926699966
SQL> set linesize 100
SQL> l
1* select * from X$KGLLK where KGLLKHDL = 'C000000122E2A6D8' order by KGLLKSNM,KGLNAOBJ
SQL> /
ADDR INDX INST_ID KGLLKADR KGLLKUSE KGLLKSES KGLLKSNM
---------------- ---------- ---------- ---------------- ---------------- ---------------- ----------
KGLLKHDL KGLLKPNC KGLLKPNS KGLLKCNT KGLLKMOD KGLLKREQ KGLLKFLG
---------------- ---------------- ---------------- ---------- ---------- ---------- ----------
KGLLKSPN KGLLKHTB KGLNAHSH KGLHDPAR KGLHDNSP USER_NAME
---------- ---------------- ---------- ---------------- ---------- ------------------------------
KGLNAOBJ
------------------------------------------------------------
800003FB0007E4D0 33 2 C00000011A449E20 C000000109F02C68 C000000109F02C68 30
C000000122E2A6D8 00 00 0 0 2 0
463 C00000011A4BC350 3990848181 C000000122E2A6D8 1 PUBUSER
CSNOZ629926699966
800003FB0007E5B0 34 2 C00000011A44A150 C000000108C99E28 C000000108C99E28 37
C000000122E2A6D8 00 00 1 3 0 0
179 C00000011A4BB328 3990848181 C000000122E2A6D8 1 PUBUSER
CSNOZ629926699966
上一个例子中我们主要借助于X$KGLLK基表和event systemstate解决问题，那么如果你不了解X$KGLLK基表，或者忘记了如何使用它，那也不要紧张，这里再介绍一种常规的方法。
从system state的转储信息中，我们已经注意到PROCESS 28当前正在等待'library cache lock'。'handle address'表示的就是正持有PROCESS 28进程所等待的library cache中的地址。
现在我们继续在跟踪文件中查找包含'handle=c000000122e2a6d8'字符串的ORACLE PROCESS，也就是查找blocking session的信息，发现信息如下：
PROCESS 26: ----------------阻塞其他会话的Oracle进程，这里PROCESS 26对应了V$PROCESS中的PID的值----------------------------------------
SO: c000000109c831e0, type: 2, owner: 0000000000000000, flag: INIT/-/-/0x00
(process) Oracle pid=26, calls cur/top: c00000010b2774d0/c00000010b2774d0, flag: (0) -
int error: 0, call error: 0, sess error: 0, txn error 0
(post info) last post received: 17 24 6
last post received-location: ksusig
last process to post me: c000000109c840f8 25 0
last post sent: 751404 0 15
last post sent-location: ksasnd
last process posted by me: c000000109c836e8 1 6
(latch info) wait_event=0 bits=0
Process Group: DEFAULT, pseudo proc: c000000109eefda0
O/S info: user: ora9i, term: UNKNOWN, ospid: 20552OSD pid info: Unix process pid: 20552, image:(TNS V1-V3)
----------------------------------------
SO: c0000001180b9510, type: 8, owner: c000000109c831e0, flag: INIT/-/-/0x00
(FOB) flags=2 fib ptr=162e1b48 incno=0 pending i/o cnt=0
----------------------------------------
SO: c0000001180b9458, type: 8, owner: c000000109c831e0, flag: INIT/-/-/0x00
(FOB) flags=2 fib ptr=162deb18 incno=0 pending i/o cnt=0
----------------------------------------
SO: c0000001180b8230, type: 8, owner: c000000109c831e0, flag: INIT/-/-/0x00
(FOB) flags=2 fib ptr=162de848 incno=0 pending i/o cnt=0
----------------------------------------
SO: c0000001180b7b00, type: 8, owner: c000000109c831e0, flag: INIT/-/-/0x00
(FOB) flags=2 fib ptr=162de578 incno=0 pending i/o cnt=0
----------------------------------------
SO: c000000108c99e28, type: 4, owner: c000000109c831e0, flag: INIT/-/-/0x00c000000108c99e28对应的就是V$SESSION中的SADDR的值，通过这个信息就可以找到blocking session的SID等信息(session) trans: c0000001169403c0, creator: c000000109c831e0, flag: (100041) USR/- BSY/-/-/-/-/-
DID: 0002-001A-0000007D, short-term DID: 0000-0000-00000000
txn branch: c00000011b825e18
oct: 0, prv: 0, sql: 800003fb0005f7b0, psql: c00000011fbe3f98, user: 50/PUBUSERO/S info: user: report16, term: , ospid: 20550, machine: cs_dc02program:(TNS V1-V3)
application name: SQL*Plus, hash value=3669949024
waiting for 'SQL*Net message from dblink' blocking sess=0x0 seq=3319 wait_time=0driver id=28444553, #bytes=1, =0-------------------这里，
#bytes表示个server process通过database link发送给另一个server process的字节数(bytes)driver id是一个10进制数，我们需要把它转化为16进制数，然后就会发现它对应于我们通过event 10046中的相应的信息：*** 2005-01-10 11:44:48.200
WAIT #1: nam='SQL*Net message from dblink' ela= 104397696 p1=675562835p2=1 p3=0
WAIT #1: nam='SQL*Net message to dblink' ela= 4 p1=675562835p2=1 p3=0
SQL> select to_char(675562835,'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX') from dual;
TO_CHAR(675562835,'XXXXXXXXXXXXXX
---------------------------------
28444553
SQL>
temporary object counter: 0
----------------------------------------
SO: c00000011a4496b0, type: 51, owner: c000000108c99e28, flag: INIT/-/-/0x00
LIBRARY OBJECT LOCK: lock=c00000011a4496b0 handle=c00000012029f968 mode=N
call pin=0000000000000000 session pin=c00000011a44ad70
htl=c00000011a449720[c00000011a4baa78,c00000011a4baa78] htb=c00000011a4baa78
user=c000000108c99e28 session=c000000108c99e28 count=1 flags=[00] savepoint=173
LIBRARY OBJECT HANDLE: handle=c00000012029f968
namespace=CRSR flags=RON/KGHP/PN0/[10010000]
kkkk-dddd-llll=0000-0041-0041 lock=N pin=0 latch#=3
lwt=c00000012029f998[c00000012029f998,c00000012029f998] ltm=c00000012029f9a8[c00000012029f9a8,c00000012029f9a8]
pwt=c00000012029f9c8[c00000012029f9c8,c00000012029f9c8] ptm=c00000012029fa58[c00000012029fa58,c00000012029fa58]
ref=c00000012029f978[c0000001202a0068, c0000001202a0068] lnd=c00000012029fa70[c00000012029fa70,c00000012029fa70]
LIBRARY OBJECT: object=c00000012029f5c8
type=CRSR flags=EXS[0001] pflags= [00] status=VALD load=0
DEPENDENCIES: count=1 size=16
AUTHORIZATIONS: count=1 size=16 minimum entrysize=16
ACCESSES: count=1 size=16
DATA BLOCKS:
data# heap pointer status pins change
----- -------- -------- ------ ---- ------
0 c00000012029f8a8 c00000012029f288 I/P/A 0 NONE
6 c00000012029f6e8 c00000012029e7c8 I/-/A 0 NONE
----------------------------------------
。。。 。。。
----------------------------------------
SO: c00000011a44a150, type: 51, owner: c0000001169403c0, flag: INIT/-/-/0x00
// X$KGLLK.KGLLKADR对应于SO(SO: c00000011a44a150 //
// X$KGLLK.KGLLKUSE和x$kgllk.KGLLKSES对应于owner的值(owner: c0000001169403c0)LIBRARY OBJECT LOCK: lock=c00000011a44a150 handle=c000000122e2a6d8 mode=X
// X$KGLLK.KGLLKADR对应于SO和lock的值(SO:c00000011a44a150,lock=c00000011a44a150) //
// X$KGLLK.KGLLKHDL对应于handle的值(handle=c000000122e2a6d8) call pin=0000000000000000 session pin=0000000000000000
// X$KGLLK.KGLLKPNS对应于session pin的值(session pin=0000000000000000) //htl=c00000011a44a1c0[c00000011a4bb328,c00000011a4bb328] htb=c00000011a4bb328user=c000000108c99e28 session=c000000108c99e28 count=1 flags=[00] savepoint=179user和session的值分别对应着x$kgllk.KGLLKUSE和x$kgllk.KGLLKSES，也对应于V$SESSION中阻塞其他会话的SADDR// X$KGLLK.KGLLKSPN对应于savepoint的值(savepoint=179) //LIBRARY OBJECT HANDLE:handle=c000000122e2a6d8
name=PUBUSER.CSNOZ629926699966
hash=eddf82b5 timestamp=01-08-2005 13:00:18 previous=NULL
namespace=TABL/PRCD/TYPE flags=KGHP/TIM/PTM/SML/[02000000]
kkkk-dddd-llll=0000-0709-0001 lock=X pin=X latch#=3
lwt=c000000122e2a708[c00000011a449e40,c00000011a449e40] ltm=c000000122e2a718[c000000122e2a718,c000000122e2a718]
pwt=c000000122e2a738[c000000122e2a738,c000000122e2a738] ptm=c000000122e2a7c8[c000000122e2a7c8,c000000122e2a7c8]
ref=c000000122e2a6e8[c000000122e2a6e8, c000000122e2a6e8] lnd=c000000122e2a7e0[c000000122e2a7e0,c000000122e2a7e0]
LOCK INSTANCE LOCK: id=LBcafc8485d0949f81
PIN INSTANCE LOCK: id=NBcafc8485d0949f81 mode=X release=F flags=[00]
LIBRARY OBJECT: object=c000000122e12f70
type=TABL flags=EXS/LOC/CRT[0015] pflags= [00] status=VALD load=0
DATA BLOCKS:
data# heap pointer status pins change
----- -------- -------- ------ ---- ------
0 c000000122e2a618 c000000122e13118 I/P/A 0 INSERT
3 c000000122e13178 0 -/P/- 1 NONE
8 c000000122e12c30 c000000122febdb8 I/P/A 1 UPDATE
9 c000000122e13090 0 -/P/- 1 NONE
10 c000000122e12ce0 c000000122acbc70 I/P/A 1 UPDATE
----------------------------------------
。。。 。。。
根据上述两个ORACLE进程号(ORACLE PID)，我们可以找到他们的会话信息和操作系统进程信息SQL> select spid,pid,addr from v$process where pid in (26,28);
SPID PID ADDR
------------ ---------- ----------------20552 26 C000000109C831E0 -----------阻塞其他会话的Oracle进程22580 28 C000000109C83BF0 -----------被阻塞的Oracle进程
SQL>
我们来进一步证实一下上述信息：
SQL>col username for a20
SQL> col osuser for a20
SQL> col machine for a20
SQL> l
1 select sid,serial#,username,osuser,machine,to_char(logon_time,'yyyy/mm/dd hh24:mi:ss') LogonTime
2* from v$session where paddr in ( select addr from v$process where spid ='&spid')
SQL> /
Enter value for spid: 20552 -----------阻塞其他会话的Oracle进程
old 2: from v$session where paddr in ( select addr from v$process where spid ='&spid')
new 2: from v$session where paddr in ( select addr from v$process where spid ='20552')
SID SERIAL# USERNAME OSUSER MACHINE LOGONTIME
---------- ---------- -------------------- -------------------- -------------------- -------------------
37 2707 PUBUSER report16 cs_dc02 2005/01/08 13:00:17
SQL> /
Enter value for spid: 22580 -----------被阻塞的Oracle进程
old 2: from v$session where paddr in ( select addr from v$process where spid ='&spid')
new 2: from v$session where paddr in ( select addr from v$process where spid ='22580')
SID SERIAL# USERNAME OSUSER MACHINE LOGONTIME
---------- ---------- -------------------- -------------------- -------------------- -------------------
30 24167 PUBUSER ora9i cs_dc02 2005/01/10 10:20:31
SQL> select sid,saddr,paddr,username,status,OSUSER from v$session where sid in (37,30);
SID SADDR PADDR USERNAME STATUS OSUSER
---------- ---------------- ---------------- -------------------- -------- --------------------30 C000000109F02C68 C000000109C83BF0 PUBUSER ACTIVE ora9i
37 C000000108C99E28 C000000109C831E0 PUBUSER ACTIVE report16
SQL>现在，问题已经水落石出了，解决方法和方法1中的一样(在操作系统中直接kill掉相应的操作系统进程)。
当然，处于研究的目的，我们可以进一步了解一下上述两个会话(SID 30和SID 37)所有已经持有锁的相关信息：SQL> set linesize 150
SQL> set pages 10000
SQL> select * from v$lock where sid in (37,30);
ADDR KADDR SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK
---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ----------
C0000001169403C0 C000000116940538 37 TX 917507 26579 6 0 1804782
C00000011676DAE0 C00000011676DB08 37 TM 18 0 3 0 1804782
C00000010B30C4E8 C00000010B30C508 37 XR 4 0 2 0 1803692
C00000010B30C460 C00000010B30C480 37 DX 21 0 1 0 68 0
SQL>不难看出，会话37阻塞了其他会话
现在，我们再进一步看看会话37当前在哪些对象上加了锁：SQL> select object_name,object_id from dba_objects where object_id in ('917507','18','4','21') order by object_id;
OBJECT_NAME OBJECT_ID
------------------------------ ----------
TAB$ 4
OBJ$ 18
COL$ 21
SQL> /
OBJECT_NAME OBJECT_ID
------------------------------ ----------
TAB$ 4
OBJ$ 18
COL$ 21
SQL>
接下来，再着重看看SID为37的会话在library cache中请求和持有对象锁的详细信息：SQL> col KGLNAOBJ for a30
SQL> col USER_NAME for a10
SQL> l
1 select INST_ID,USER_NAME,KGLNAOBJ,KGLLKSNM,KGLLKUSE,KGLLKSES,KGLLKMOD,KGLLKREQ
2* from x$kgllk where KGLLKSNM = 37
SQL> /
INST_ID USER_NAME KGLNAOBJ KGLLKSNM KGLLKUSE KGLLKSES KGLLKMOD KGLLKREQ
---------- ---------- ------------------------------ ---------- ---------------- ---------------- ---------- ----------
2 PUBUSER DBMS_OUTPUT 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER DBMS_OUTPUT 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER DBMS_STANDARD 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER PUBUSER 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER SELECT MINOR_VERSION FROM SY 37 C000000108C99E28 C000000108C99E28 1 0
S.CDC_SYSTEM$
2 PUBUSER SELECT MINOR_VERSION FROM SY 37 C000000108C99E28 C000000108C99E28 1 0
S.CDC_SYSTEM$
2 PUBUSER DBMS_CDC_PUBLISH 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER DBMS_CDC_PUBLISH 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER CSNOZ629926699966 37 C000000108C99E28 C000000108C99E28 3 0
2 PUBUSER DBMS_APPLICATION_INFO 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER DBMS_APPLICATION_INFO 37 C000000108C99E28 C000000108C99E28 1 0
2 PUBUSER DATABASE 37 C000000108C99E28 C000000108C99E28 1 0
12 rows selected.
SQL>
再看看SID为30的会话在library cache中请求和持有对象锁的详细信息：SQL> select INST_ID,USER_NAME,KGLNAOBJ,KGLLKSNM,KGLLKUSE,KGLLKSES,KGLLKMOD,KGLLKREQ
2 from x$kgllk where KGLLKSNM = 30
3 /
INST_ID USER_NAME KGLNAOBJ KGLLKSNM KGLLKUSE KGLLKSES KGLLKMOD KGLLKREQ
---------- ---------- ------------------------------ ---------- ---------------- ---------------- ---------- ----------
2 PUBUSER PUBUSER 30 C000000109F02C68 C000000109F02C68 1 0
2 PUBUSER CSNOZ629926699966 30 C000000109F02C68 C000000109F02C68 0 2
2 PUBUSER DBMS_APPLICATION_INFO 30 C000000109F02C68 C000000109F02C68 1 0
2 PUBUSER DBMS_APPLICATION_INFO 30 C000000109F02C68 C000000109F02C68 1 0
2 PUBUSER DATABASE 30 C000000109F02C68 C000000109F02C68 1 0
SQL>
KGLNAOBJ列包含了在librarky cache中的对象上执行命令的语句的前80个字符，其实从这里我们也可以大大缩小范围了KGLLKSES对应于V$SESSION中的SADDR列的值KGLLKSNM对应于V$SESSION中的SID(Session ID)
KGLLKHDL的值与方法1中跟踪文件中的'handle address'的值对应KGLLKPNS的值对应于方法1中跟踪文件中的'Ssession pin'的值
SQL> set linesize 2000
SQL> l
1 select INST_ID,USER_NAME,KGLNAOBJ,KGLLKSNM,KGLLKUSE,KGLLKSES,KGLLKMOD,KGLLKREQ,KGLLKPNS,KGLLKHDL
2* from x$kgllk where KGLLKSNM in (30,37) order by KGLLKSNM,KGLNAOBJ
SQL> /
INST_ID USER_NAME KGLNAOBJ KGLLKSNM KGLLKUSE KGLLKSES KGLLKMOD KGLLKREQ KGLLKPNS KGLLKHDL
---------- ------------------------------ ------------------------------------------------------------ ---------- ---------------- ---------------- ---------- ---------- ---------------- ----------------
2 PUBUSER DATABASE 30 C000000109F02C68 C000000109F02C68 1 0 00 C000000119F8EC58
2 PUBUSER DBMS_APPLICATION_INFO 30 C000000109F02C68 C000000109F02C68 1 0 00 C00000011CCDDA48
2 PUBUSER DBMS_APPLICATION_INFO 30 C000000109F02C68 C000000109F02C68 1 0 00 C00000011CCD81B8
2 PUBUSER PUBUSER 30 C000000109F02C68 C000000109F02C68 1 0 00 C00000011CBFDAA8
2 PUBUSER CSNOZ629926699966 30 C000000109F02C68 C000000109F02C68 0 2 00 C000000122E2A6D8
2 PUBUSER DATABASE 37 C000000108C99E28 C000000108C99E28 1 0 00 C000000119F8EC58
2 PUBUSER DBMS_APPLICATION_INFO 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011CCDDA48
2 PUBUSER DBMS_APPLICATION_INFO 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011CCD81B8
2 PUBUSER DBMS_CDC_PUBLISH 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011FEA4918
2 PUBUSER DBMS_CDC_PUBLISH 37 C000000108C99E28 C000000108C99E28 1 0 00 C0000001202A4988
2 PUBUSER DBMS_OUTPUT 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011CCB48B0
2 PUBUSER DBMS_OUTPUT 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011FFF5098
2 PUBUSER DBMS_STANDARD 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011CCF0ED8
2 PUBUSER PUBUSER 37 C000000108C99E28 C000000108C99E28 1 0 00 C00000011CBFDAA8
2 PUBUSER SELECT MINOR_VERSION FROM SYS.CDC_SYSTEM$ 37 C000000108C99E28 C000000108C99E28 1 0 C00000011A44AD70 C00000012029F968
2 PUBUSER SELECT MINOR_VERSION FROM SYS.CDC_SYSTEM$ 37 C000000108C99E28 C000000108C99E28 1 0 00 C0000001202A0228
2 PUBUSER CSNOZ629926699966 37 C000000108C99E28 C000000108C99E28 3 0 00 C000000122E2A6D8
17 rows selected.
SQL>
前面我们已经知道碰到'library cache lock'导致进程hang时，如何解决。
那么如何避免这类问题的发生呢？这篇文章主要介绍了library cache lock的成因以及如何避免。
当我们在执行一些DML，DDL，甚至desc tablename等等操作的时候，会话就hang住了，还有一种情况，当我们使用create or replace procedure/function等语句修改Procedure和Function的时候，会话也会hang住，这是为什么呢？
当出现上述情况的时候，我们可以通过v$session_wait查询等待事件，当然，这种情况下，该session的等待事件一定是'Library cache lock'。
让我们来解释一下，
第 一种情况，当会话1(session 1)在对一个表执行DML或者DDL，与此同时还有另一个会话，我们姑且称之为会话2(session 2)，这个会话2也在对这个表执行DDL(如ALTER TABLE)，当会话2的完成需要很长时间时(依操作的具体的数据量而定)，会话1就会hang住，这时，你查询会话1的等待事件就是'Library cache lock'。
第二种情况，当会话1(session 1)在修改一个package，与此同时还有另一个会话，我们姑且称之为会话2(session 2)，这个会话2正在执行会话1所修改的package中的Procedure或者Function，会话1就会hang住，这时，你查询会话1的等待事 件就是'Library cache lock'。
因此，在对Package/Procedure/Function/View进行编译和分析的时候，我们必须确定此时没有人正在编译和分析相同的对象，即确保没有人也在此时改变这些需要重定义(drop和recreate)的对象的定义。
SQL> create or replace procedure who_is_using wrapped
2 0
3 abcd
4 abcd
5 abcd
6 abcd
7 abcd
8 abcd
9 abcd
10 abcd
11 abcd
12 abcd
13 abcd
14 abcd
15 abcd
16 abcd
17 abcd
18 abcd
19 7
20 200f000
21 1
22 4
23 0
24 1e
25 c WHO_IS_USING:
26 8 OBJ_NAME:
27 8 VARCHAR2:
28 b DBMS_OUTPUT:
29 6 ENABLE:
30 7 1000000:
31 1 I:
32 1 B:
33 8 USERNAME:
34 3 SID:
35 3 SYS:
36 7 X$KGLPN:
37 1 A:
38 9 V$SESSION:
39 7 X$KGLOB:
40 1 C:
41 8 KGLPNUSE:
42 1 =:
43 5 SADDR:
44 5 UPPER:
45 8 KGLNAOBJ:
46 4 LIKE:
47 8 KGLPNHDL:
48 8 KGLHDADR:
49 4 LOOP:
50 8 PUT_LINE:
51 1 (:
52 2 ||:
53 7 TO_CHAR:
54 4 ) - :
55 0
56
57 0
58 0
59 74
60 2
61 0 1d 9a 8f a0 b0 3d b4
62 55 6a :2 a0 6b 51 a5 57 91
63 :2 a0 6b :2 a0 6b ac :2 a0 6b a0
64 b9 :2 a0 b9 :2 a0 6b a0 b9 b2
65 ee :2 a0 6b a0 7e a0 6b b4
66 2e :3 a0 6b a5 b 7e :2 a0 a5
67 b b4 2e a 10 :2 a0 6b a0
68 7e a0 6b b4 2e a 10 ac
69 d0 e5 e9 37 :3 a0 6b 6e 7e
70 :3 a0 6b a5 b b4 2e 7e 6e
71 b4 2e 7e :2 a0 6b b4 2e a5
72 57 b7 a0 47 b7 a4 b1 11
73 68 4f 17 b5
74 74
75 2
76 0 3 4 19 15 14 20 13
77 25 29 2d 31 35 38 3b 3c
78 41 45 49 4d 50 54 58 5b
79 5c 60 64 67 11 6b 6f 73
80 75 79 7d 80 84 86 87 8e
81 92 96 99 9d a0 a4 a7 a8
82 ad b1 b5 b9 bc bd bf c2
83 c6 ca cb cd ce 1 d3 d8
84 dc e0 e3 e7 ea ee f1 f2
85 1 f7 fc fd 101 106 10b 10d
86 111 115 119 11c 120 123 127 12b
87 12f 132 133 135 136 13b 13e 142
88 143 148 14b 14f 153 156 157 15c
89 15d 162 164 168 16f 171 175 177
90 182 186 188 18f
91 74
92 2
93 0 1 b 18 21 :2 18 17 :2 1
94 2 :2 e 15 :2 2 6 1c :2 1e 27
95 :2 29 1c 11 15 11 1d 11 1f
96 29 1f 2b 2f 2b 37 2b c
97 11 12 :2 14 1f 1d :2 21 :2 1d 12
98 18 :2 1a :3 12 2a 30 :2 2a :5 12 :2 14
99 1f 1d :2 21 :2 1d :2 12 :4 c 2 2b
100 3 :2 f 18 1b 1d 25 :2 27 :2 1d
101 :2 18 2b 2d :2 18 33 35 :2 37 :2 18
102 :2 3 2b 6 2 :8 1
103 74
104 2
105 0 :9 1 :6 3 :8 4 :f 5 :9 6 :d 7 :2 6
106 :9 8 :2 6 5 :4 4 8 :19 9 8 a
107 4 :2 2 :6 1
108 191
109 2
110 :4 0 1 :a 0 70 1 1a 1b 5
111 :2 3 :3 0 2 :6 0 5 4 :3 0 7
112 :2 0 70 2 8 :2 0 4 :3 0 5
113 :3 0 a b 0 6 :2 0 7 c
114 e :2 0 6c 7 :3 0 8 :3 0 9
115 :3 0 11 12 0 8 :3 0 a :3 0
116 14 15 0 9 b :3 0 c :3 0
117 18 19 0 d :3 0 e :3 0 8
118 :3 0 1d 1e b :3 0 f :3 0 20
119 21 0 10 :3 0 22 23 c 25
120 49 0 4a :3 0 d :3 0 11 :3 0
121 27 28 0 8 :3 0 12 :2 0 13
122 :3 0 2a 2c 0 12 2b 2e :3 0
123 14 :3 0 10 :3 0 15 :3 0 31 32
124 0 10 30 34 16 :2 0 14 :3 0
125 2 :3 0 15 37 39 17 36 3b
126 :3 0 2f 3d 3c :2 0 d :3 0 17
127 :3 0 3f 40 0 10 :3 0 12 :2 0
128 18 :3 0 42 44 0 1c 43 46
129 :3 0 3e 48 47 :3 0 2 17 26
130 0 4b :5 0 4c :2 0 4e 10 4d
131 19 :3 0 4 :3 0 1a :3 0 50 51
132 0 1b :3 0 1c :2 0 1d :3 0 7
133 :3 0 a :3 0 56 57 0 1a 55
134 59 1f 54 5b :3 0 1c :2 0 1e
135 :3 0 22 5d 5f :3 0 1c :2 0 7
136 :3 0 9 :3 0 62 63 0 25 61
137 65 :3 0 28 52 67 :2 0 69 2a
138 6b 19 :3 0 4e 69 :4 0 6c 2c
139 6f :3 0 6f 0 6f 6e 6c 6d
140 :6 0 70 0 2 8 6f 72 :2 0
141 1 70 73 :6 0
142 2f
143 2
144 :3 0 1 3 1 6 1 d 2
145 13 16 3 1c 1f 24 1 33
146 2 29 2d 1 38 2 35 3a
147 1 58 2 41 45 2 53 5a
148 2 5c 5e 2 60 64 1 66
149 1 68 2 f 6b
150 1
151 4
152 0
153 72
154 0
155 1
156 14
157 2
158 3
159 0 1 0 0 0 0 0 0
160 0 0 0 0 0 0 0 0
161 0 0 0 0
162 2 0 1
163 3 1 0
164 10 2 0
165 0
166 /
Procedure created.
Elapsed: 00:00:00.07
SQL>