January 31, 2011 at 2:08 pm
I may be wrong but from what I remembered, a database snapshot stores original values into sparse files of any changes in the databases (correct me if I'm wrong).
To query a mirrored databases you first create a snapshot of it. However I'm not sure how that works because if you create a snapshot and nothing changed then how would it work? I'm thinking my understanding may be wrong and maybe a snapshot is a copy of an entire database?
Thanks!
January 31, 2011 at 2:13 pm
Snapshots are copies of the whole thing.
Check data here for details: http://msdn.microsoft.com/en-us/library/ms187054(SQL.90).aspx
- Gus "GSquared", RSVP, OODA, MAP, NMVP, FAQ, SAT, SQL, DNA, RNA, UOI, IOU, AM, PM, AD, BC, BCE, USA, UN, CF, ROFL, LOL, ETC
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January 31, 2011 at 2:17 pm
Ok so when I create a snapshot of a regular standalone database and then delete a record in that database then the change will be at the database and if i wanted to bring that record back then i would just do a select it form the snapshot?
thanks!
January 31, 2011 at 10:10 pm
Hi ,
The answer for your question is Yes.
When the snapshot is taken you can see the data at the point of time of your source databases.
When the modification is happening at the sources databases , the original data (Old) will moved to snapshot data file. then the changed data (New) will be applied in the Source databases.
in your case you are deleting the rows from the particular table, before deleting the records from the source database it will move the original data into snapshot data file and then delete them from the source database.
Hope this helps.
Regards,
Subbu
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January 31, 2011 at 10:14 pm
Please refer the link posted by GSquared.
Below are the points from the link.
"Before a page of the source database is modified for the first time, the original page is copied from the source database to the snapshot. To store the copied original pages, the snapshot uses one or more sparse files.After a page has been updated, a read operation on the snapshot still accesses the original page, which is now stored in a sparse file."
Once update happens, you would be reading the contents from the snapshot db which internally stores the original data in a sparse file.
M&M
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