请教：关于利用数据链路建表死锁的问题？

Yong Huang

最初由 blue 发布
[B]
metalink
note 53711.996
...
From: Oracle, Melissa Holman 15-Jan-01 21:43
Subject: Re : PMON cleanup

Cate,

PMON is cleaning up and rolling back all uncommitted transactions every 3 minutes and this is not configurable.
...
[/B]

I searched all other places but couldn't find any other reference to this 3 minute rule. That just doesn't sound right. According to Steve Adams, if you alter system kill session, that session will rollback its transaction. But if at this moment, you kill the shadow process for this session, PMON will take over the rollback task. That's probably what Melissa Holman was referring to. But where on earth did she get this 3 minute rule? PMON wakes up every 3 seconds to see if there's any work to do (wait event: pmon timer). If there is, it constantly does its work instead of sleeping and waiting on its timer. Melissa's message is not clear on this. Does it check every 3 minutes (which is wrong)? Does it clean up for some time shorter than 3 minutes and go to sleep for either 3 minutes, or 3 minutes minus the time it just did the cleanup? I mean, say it does the cleanup for e.g. 30 seconds, then it sleeps for 180 seconds, cleans up again for 30 seconds, sleeps for another 180 seconds? Or cleans up for 30 seconds, sleeps 150 seconds (so the total is 3 minutes)? Quite confusing.

Yong Huang

blue

最初由 Yong Huang 发布
[B]

I searched all other places but couldn't find any other reference to this 3 minute rule. That just doesn't sound right. According to Steve Adams, if you alter system kill session, that session will rollback its transaction. But if at this moment, you kill the shadow process for this session, PMON will take over the rollback task. That's probably what Melissa Holman was referring to. But where on earth did she get this 3 minute rule? PMON wakes up every 3 seconds to see if there's any work to do (wait event: pmon timer). If there is, it constantly does its work instead of sleeping and waiting on its timer. Melissa's message is not clear on this. Does it check every 3 minutes (which is wrong)? Does it clean up for some time shorter than 3 minutes and go to sleep for either 3 minutes, or 3 minutes minus the time it just did the cleanup? I mean, say it does the cleanup for e.g. 30 seconds, then it sleeps for 180 seconds, cleans up again for 30 seconds, sleeps for another 180 seconds? Or cleans up for 30 seconds, sleeps 150 seconds (so the total is 3 minutes)? Quite confusing.

Yong Huang [/B]

楼上老兄考虑得很仔细，你说的也是对的
在asktom上，有有关的faq
A simple doubt:
Oracle Documentation (Oracle Concepts) says:
"Like SMON, PMON wakes up regularly to check whether it is needed, and can be
called if another process detects the need for it."What does "regularly" mean?
Every seconnd? Milisecond?

Thank you very much!!!

Followup:  
about every 3 seconds

http://asktom.oracle.com/pls/ask ... 42376742,%7Bpmon%7D

chucknancy

慢慢消化！

homesite

设置手册：各种系统都有
http://www.sybase.com.cn/cn/cont ... c_pb_dbms_00005.htm

lwxxrq

你们讨论的好深奥哦，我有一次也碰到这种事：
create table tablename as select * from tablename@db_link;
结果执行了4个小时也没反应，好像死了，但sqlplus又可以很顺利地关掉，再运行一样的！也不报错，就停着。最让人晕的是，只有这个表会这样！别的表都几秒钟就OK了！shit ！
真不爽啊，结果后来偶然发现客户机装着趋势防毒的防火墙，把防火墙关掉再试，立刻OK！！
我就不明白，为什么它别的表又可以顺利创建？这个不行创建的表虽然是最大的，但也不过十几MB而已！晕...