死锁（ora-00060）以及死锁相关的知识点
最近碰到一个死锁的问题：ora-00060 deadlock detected while waiting for resource （ora-00060 等待资源时检测到死锁）
查看udump（SQL> show parameter USER_DUMP_DEST; 查看该目录）下面的trace，发现如下日志：
*** 2009-08-13 10:53:11.656
*** SERVICE NAME:(his3) 2009-08-13 10:53:11.593
*** SESSION ID:(130.3437) 2009-08-13 10:53:11.593
DEADLOCK DETECTED
[Transaction Deadlock]
Current SQL statement for this session:
UPDATE MY_KUCUN1 SET KUCUNSL = KUCUNSL - :B3 WHERE YINGYONGID = :B2 AND JIAGEID = :B1
----- PL/SQL Call Stack -----
object line object
handle number name
33DF6A44 6002 package body HIS3KS.PKG_MY_JINXIAOCUN
2FD11B48 1 anonymous block
The following deadlock is not an ORACLE error. It is a
deadlock due to user error in the design of an application
or from issuing incorrect ad-hoc SQL. The following
information may aid in determining the deadlock:
Deadlock graph:
---------Blocker(s)-------- ---------Waiter(s)---------
Resource Name process session holds waits process session holds waits
TX-000b001c-00005019 38 130 X 19 106 X
TX-00010025-000100ee 19 106 X 38 130 X
session 130: DID 0001-0026-00008297 session 106: DID 0001-0013-00004EB8
session 106: DID 0001-0013-00004EB8 session 130: DID 0001-0026-00008297
Rows waited on:
Session 106: obj - rowid = 0000E1AB - AAAOGrAAXAAAJHQAAT
(dictionary objn - 57771, file - 23, block - 37328, slot - 19)
Session 130: obj - rowid = 0000E1AB - AAAOGrAAXAAAJHQAAZ
(dictionary objn - 57771, file - 23, block - 37328, slot - 25)
Information on the OTHER waiting sessions:
Session 106:
pid=19 serial=671 audsid=309881 user: 64/HIS3KS
O/S info: user: NT AUTHORITY/ANONYMOUS LOGON, term: MEDIINFO-QA2, ospid: 6708:6612, machine: WORKGROUP/MEDIINFO-QA2
program: cicsas.exe
application name: cicsas.exe, hash value=0
Current SQL Statement:
UPDATE MY_KUCUN1 SET KUCUNSL = KUCUNSL - :B3 WHERE YINGYONGID = :B2 AND JIAGEID = :B1
End of information on OTHER waiting sessions.
===================================================
几个重要的信息就是锁的类型是X，说明是DML语句导致的行级排他锁，涉及到两个Session：130和106。130就是报错ora-00060的Session。
下面是两个Session涉及到的对象ID，三种颜色其实代表的都是同样的意思。0000E1AB的10进制就是57771
SQL> select dbms_rowid.rowid_object( 'AAAOGrAAXAAAJHQAAT' ) from dual;
DBMS_ROWID.ROWID_OBJECT('AAAOGrAAXAAAJHQAAT')
------------------------------
57771
SQL> select dbms_rowid.rowid_object( 'AAAOGrAAXAAAJHQAAZ' ) from dual;
DBMS_ROWID.ROWID_OBJECT('AAAOGrAAXAAAJHQAAZ')
------------------------------
57771
查找对象：
SQL> SELECT t.owner,t.object_name,t.object_type FROM all_objects t WHERE t.data_object_id = 57771
以上就是该日志文件能够提供的内容，可以从中分析在那个代码里面产生的问题，下面是关于死锁的知识:
1. 产生死锁的典型原理：
session A locks row X
sesssion B locks row Y
session A tries to lock row Y
session B tries to lock row X
Session A fails after roughly 3 seconds with a deadlock ORA-00060
2.死锁产生的二大原因
a. unindexed foreign keys in a system that issues a delete against the parent table OR updates the
parent primary key.
b. use of bitmap indexes on tables that are modifed "in real time".
the next big one:
c. application design flaw
the last, mostly rare - but can happen
d. itl deadlocks, undersized initrans
3. 死锁产生后，其中一个占用资源会被Oracle自动释放，例如：
just set up a table with three rows (x=1,2,3)
in 3 sessions - update 1 and then 2 and then 3 (one in each session)
have session 3 update 1
have session 2 update 3
have session 1 update 2
one of them will be chosen as the deadlock victim and their STATEMENT (but not transaction) will be
rolled back, they have to figure out whether to go forward and eventually commit or rollback the
transaction, releasing one of the other sessions.
That means multiple way deadlocks are resolved by killing the transactions by oracle as if
deadlocks are between two transactions until all the deadlocks are cleared.
but in a distributed environment, things are different (the locks time out instead).
4. session deadlock itself 单个session也可以产生死锁
create table t ( x int primary key );
insert into t values ( 1 );
declare
pragma autonomous_transaction;
begin
insert into t values ( 1 );
commit;
end;
/
that'll do it. all you need is two transactions and you have that ability.
参考资料：
http://www.oracle.com.cn/viewthread.php?tid=140645
http://it.toolbox.com/blogs/confessions/how-to-use-oracle-25-understanding-deadlocks-17029
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:4144238660486
http://asktom.oracle.com/pls/asktom/f?p=100:11:8973480827671230::::P11_QUESTION_ID:1068032649872