January 15, 2011 at 11:41 am
Nice easy question, nice clean answer.
But why on earth is it worth 2 points?
Tom
January 15, 2011 at 5:02 pm
I wasn't thinking it was easy for many people. Also, restores are critical.
January 16, 2011 at 2:41 am
Great question.
I had to do some research to rule out extent, so I definately learned something.
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My blog at https://sqlkover.com.
MCSE Business Intelligence - Microsoft Data Platform MVP
January 16, 2011 at 3:24 am
Tom.Thomson (1/15/2011)
Nice easy question, nice clean answer.But why on earth is it worth 2 points?
Want to take a guess how many get page and extent wrong?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
January 16, 2011 at 9:33 am
As of the time of this posting (20 attempts) 55% of the answers are incorrect - appallingly high, of those 10 % or (2 indiviuals) selected extents .
So once again the QOD becomes a teaching tool.
But now with this and prior posting to this forum I would expect the percentage of correct answers to increase.
January 16, 2011 at 9:56 am
bitbucket-25253 (1/16/2011)
As of the time of this posting (20 attempts) 55% of the answers are incorrect - appallingly high, of those 10 % or (2 indiviuals) selected extents .
I'm not particularly surprised. Seeing how often backups get messed up, I'd be surprised if restores were well know.
Maybe I'm just been pessimistic and cynical again...
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
January 17, 2011 at 8:35 am
Steve,
An extent is nothing more that a group of eight contiguous database pages.
Since Page restore can be used to restore one or more damaged pages, it can restore any extent also.
I do understand there is no "Restore Extent" command, but if you know what one is you could restore it with the right recovery level and Server version that supports it.
January 17, 2011 at 8:46 am
Nice one - looks like I was one of many who didn't realise you could restore at the page level. I'll certainly look into this as it's the kind of thing you want to know in an emergency. Shame that like most useful SQL functionality, online restore of pages requires Enterprise Edition :exclamation:
January 17, 2011 at 3:32 pm
bitbucket-25253 (1/16/2011)
So once again the QOD becomes a teaching tool.
Not certain who is learning.
Restoring a group of pages can restore an extent.
Are all the answers actual Restore command types as listed in the refference article?
January 17, 2011 at 10:49 pm
SanDroid (1/17/2011)
Not certain who is learning.Restoring a group of pages can restore an extent.
There is no RESTORE DATABASE ... EXTENT command. There is a RESTORE DATABASE ... FILEGROUP, a RESTORE DATABASE ... FILE and a RESTORE DATABASE ... PAGE
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
January 18, 2011 at 1:37 am
jts_2003 (1/17/2011)
Shame that like most useful SQL functionality, online restore of pages requires Enterprise Edition :exclamation:
They must have some reason to sell the more expensive version 🙂
Need an answer? No, you need a question
My blog at https://sqlkover.com.
MCSE Business Intelligence - Microsoft Data Platform MVP
January 18, 2011 at 11:48 am
So, now I know you can restore a page. However, I don't see how this could be used practically with confidence.
How do you know when your restore a page that you've not compromised relational data? For example, in a parent/child scenario, what if a new parent record with associated child records were added since the page was last backed up. If parent record was part of the page that was restored over and the children were not, then this would orphan the child records.
Help me understand this better.
January 18, 2011 at 12:01 pm
Del Lee (1/18/2011)
So, now I know you can restore a page. However, I don't see how this could be used practically with confidence.
Database corruption. Restore the entire database vs restore a small number of corrupt pages? Easy decision if it's a large DB
How do you know when your restore a page that you've not compromised relational data? For example, in a parent/child scenario, what if a new parent record with associated child records were added since the page was last backed up.
You can't restore it to an earlier point in time to the rest of the DB. You have to restore the page from full backup then restore log backups to get it back to the same point that the rest of the DB is. Same as when restoring files or filegroups
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
January 18, 2011 at 12:14 pm
The engine knows you are restoring a page, so the entries from the log backups for that page only are applied to ensure relational integrity. Same for a file restore.
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