r' where age = 1" <--申请锁LOCK1,hang住,因为LOCK1被session 1持有
session 1
---------
$ db2 +c "update student set name = 'three' where age = 4" <--申请锁LOCK2,hang住,因为LOCK2被session 2持有
这时已经发生了死锁,10s之后,这两个session有一个会报出如下死锁(reason code 2)错误,另一个session成功执行
SQL0911N The current transaction has been rolled back because of a deadlock
or timeout. Reason code "2". SQLSTATE=40001
参考资料:
标准表的锁定方式和存取方案,这里您可以看到详细的加锁方式
http://www-01.ibm.com/support/knowledgecenter/SSEPGG_9.7.0/com.ibm.db2.luw.admin.perf.doc/doc/r0005275.
html lang=zh
附,只能在发生死锁或者锁等待的时候才能用db2pd查看锁的信息。下面附上如何采用事件监控器监控死锁/锁超时。事件监控器可以抓取一段时间内的锁事件
db2 update db cfg for sample using MON_LOCKWAIT hist_and_values MON_DEADLOCK hist_and_values MON_LOCKTIMEOUT hist_and_values MON_LW_THRESH 10000
db2 "CREATE EVENT MONITOR LOCKEVMON FOR LOCKING WRITE TO UNFORMATTED EVENT TABLE (TABLE LOCKEVMON)"
db2 set event monitor LOCKEVMON state=1
重现问题
db2 flush event monitor LOCKEVMON
db2 set event monitor LOCKEVMON state=0
cp /home/db2users/e97q6c/sqllib/samples/java/jdbc/db2evmonfmt.java ./
cp /home/db2users/e97q6c/sqllib/samples/java/jdbc/
DB2EvmonLocking.xsl ./
export PATH=/home/db2users/e97q6c/sqllib/java/jdk64/bin:$PATH
javac db2evmonfmt.java
java db2evmonfmt -d qsmiao -ue LOCKEVMON -ftext -u e97q6c -p e97q6c > deadlock.txt
more deadlock.txt 可以看到有关的SQL语句。
请参考
http://www.ibm.com/developerworks/cn/data/library/techarticles/dm-1004lockeventmonitor/
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