请高手指点，关于Enqueue ，ci

biti_rainy

18 Object reuse request

这个倒看来和 truncate 有点关系

yhm1229

另外id2字段的值为5

Yong Huang

最初由 biti_rainy 发布
[B]18 Object reuse request

这个倒看来和 truncate 有点关系 [/B]

How do you know he's using 8i instead of 8 or 7? (Some people never learn to provide version number when they ask questions.) To me, object reuse does not sound as closely related to truncate as flush blocks in object does (When you truncate, buffer cache blocks belonging to that object are flushed from buffer cache.) But it seems to make sense if you think of the fact that truncate table changes dba_objects.data_object_id, so "object reuse" probably means data_object_id reuse? Just guessing.

By the way, yhm1229's quote is from Metalink Note:34631.1. (We should all be more aware of copyright laws.)

Yong Huang

biti_rainy

因为实际上我并不清楚oracle的truncate
在oracle 7 中是没有data_object_id 的概念的

在8开始有的，我在想，truncate 之后 object_id没变，只是data_object_id 变了，是否可以理解为 reuse  object_id

yhm1229

数据库版本8.1.7.4

Yong Huang

最初由 biti_rainy 发布
[B]...
我在想，truncate 之后 object_id没变，只是data_object_id 变了，是否可以理解为 reuse  object_id [/B]

That may be right. I don't know why I said "object reuse" meant DATA_object_id reuse.

I'm not sure about the reason Oracle is designed this way to increment data_object_id (used by seg$ or physical segments) when you truncate. If you alter table move, both data_object_id and file_id/block_id change, which makes sense. But changing data_object_id (essentially assigning a new segment number) without physically moving location in the datafile is beyond me.

To yhm1229: Thanks for telling us your version. As I said earlier, CI locks are just side effects in your case. Focus on real issues. If you have many truncates, ask whether they're necessary.

Yong Huang

yhm1229

谢谢

d.c.b.a

以前我在搞MYDUL时发现, TRUNCATE操作实际上是分配一个新的段, 而truncate ... reuse storage才只是获得一个新的data_object_id和更新一下segment header中的一些信息.

yhm1229

最初由 d.c.b.a 发布
[B]以前我在搞MYDUL时发现, TRUNCATE操作实际上是分配一个新的段, 而truncate ... reuse storage才只是获得一个新的data_object_id和更新一下segment header中的一些信息. [/B]

谢谢！
truncate table 和truncate 。。。。reuse storage 到底在字典管理的方式下性能有多大的区别？因为enque已经成为影响生产系统的一个主要因素！

oraclerain

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