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Corruption and PAGE_VERIFY CHECKSUM


Corruption and PAGE_VERIFY CHECKSUM

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DCF
DCF
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Hi,

We've been having sporadic cases of corruption. The tables vary but the message is consistent:

Msg 605, Level 21, State 3, Line 1
Attempt to fetch logical page (5:537) in database 47 failed. It belongs to allocation unit 72057602025521152 not to 72057602063532032.


When I inspect the tables using DBCC IND and DBCC PAGE I can see that, for example, page 5:537 does have an incorrect allocation unit in it's header (as compared to the IAM page).

Yes, most sources state that most corruption is caused by I/O sub-system, but in our situation we need to prove this.


On this ms page http://support.microsoft.com/kb/2015739 it reads:

Ensure you have the PAGE_VERIFY=CHECKSUM database option turned on. While it is possible to still encounter a Msg 605 error with checksum enabled (Ex. "scribbler" problem or incorrect page provided from I/O system), enabling checksum can provide definitive proof that the page was modified incorrectly within the I/O system.


Could anyone explain to me how this provides definitive proof? Definitive proof would be very helpful in our case!

Thanks
GilaMonster
GilaMonster
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Do you have page verify set to CheckSum?

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

We walk in the dark places no others will enter
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DCF
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Yes I've verified that is the case.

I can't find any 824 errors in the logs though. Ermm
GilaMonster
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Was the database created in SQL 2005/2008?
If you check the page (via DBCC Page), what's the value for the m_flagBits setting?

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

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


DCF
DCF
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m_flagBits = 0x220
DCF
DCF
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Sorry, created in SQL 2008 R2...
GilaMonster
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Apparently there are some known bugs that cause this (error 605 with no 824). I was told to search google.

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

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


DCF
DCF
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Interesting, thanks.

I have seen the bug about inserting in to a Temp table but pretty much ruled that out.

I'll see what I can find.
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