关于SCN的理解，请指正

Yong Huang

原帖由 xuming_11 于 2009-8-28 21:56 发表
看完了，果然是高深，不过我还有一些疑惑，
期望biti_rainy等各路神仙能帮我看看问题关于SCN的疑惑，谢谢
链接如下：
http://www.itpub.net/thread-1209734-1-1.html

I read the thread in that forum. You're asking under what condition you'll have a datafile whose datafile status is online and the file is read write and yet the datafile checkpoint SCN (in controlfile) is lower than the database checkpoint. There's one scenario I can think of. You put a tablespace in backup mode and checkpoint. The datafiles in the tablespace in the backup mode will have the SCN's frozen. Here's my test (in 10.2.0.1, but should be version independent):

alter tablespace ts begin backup;
set numw 12
select file#,status,enabled,d.checkpoint_change# d_ckpt,f.checkpoint_change# f_ckpt from v$database d,v$datafile f order by 4,5;
alter system checkpoint;
select file#,status,enabled,d.checkpoint_change# d_ckpt,f.checkpoint_change# f_ckpt from v$database d,v$datafile f order by 4,5;
select * from v$backup where status = 'ACTIVE';
alter tablespace ts end backup;

Other than this, maybe Metalink Note:209329.1 helps.

Yong Huang

[ 本帖最后由 Yong Huang 于 2009-8-30 08:49 编辑 ]

0753zhongwei

学习了，谢谢。。。

liujinqi110

收益非浅！谢谢

dssi

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MicroJoey

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