Monday, January 14, 2013 1:54 PM
In the database mirroring, I understand the "possible data loss" with high-performance mode(asynchronous).
But I don't understand why we can have "possible data loss" with high-safety mode when principal server is lost ?
In high-safety mode, transaction committed on the principal are also committed on the mirror.
Do you have an idea ?
Monday, January 14, 2013 3:01 PMRead this article http://msdn.microsoft.com/en-us/library/ms189977(v=sql.105).aspx
Best Regards,Uri Dimant SQL Server MVP, http://sqlblog.com/blogs/uri_dimant/
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- Proposed As Answer by Sean GallardyMicrosoft Community Contributor, Editor Monday, January 14, 2013 5:10 PM
- Marked As Answer by Maggie LuoMicrosoft Contingent Staff, Moderator Tuesday, January 22, 2013 8:30 AM
Monday, January 14, 2013 6:41 PM
Yes, I read it.
But I still understand why ?
principal do not applied change on datafile until it's write in transaction log of the mirror.
So, if principal crashed, the transaction not written to the mirror will be rollback on the old principal when it will come back.
So the data will not be lost because they will not be applied on old principal.
missing something ?
Monday, January 14, 2013 8:15 PMAnswerer
You're assuming that the mirroring session is always 'synchronized' but in the case of what you're asking, it happens - as stated in the article - that this is only possible during the 'synchronizing' state. This is possible as the mirror was synchronizing but not yet synchronized when a forced failover occurs.
Tuesday, January 15, 2013 4:15 PM
Thanks for your answer.
This article(mirror,mirror) explain that:http://technet.microsoft.com/en-us/magazine/hh334997.aspx