Is this true?

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Is this true?

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Sachin Nandanwar SSCertifiable Points: 7699 More actions · Answer 1

hi, sachin nandawar!!!
i'm sorry, the time that i stay without post!! I was having problems with my work!
with relation the book - SQL Server 2008 Internals, this link: http://www.amazon.com/Microsoft%C2%AE-SQL-Server%C2%AE-2008-Internals/dp/0735626243 you can see the book that i said!!!
this book have e-books version for download!!!

Hi Ferrari,

No issues.I will try the book you suggested.

Thank you for your replies.

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I am just an another naive wannabe DBA trying to learn SQL Server

Jared SSC Guru Points: 61793 More actions · Answer 2

I don't see any updates in the errata for the book on this.

Let me maybe rephrase the question based on the book:

Paragraph begins saying: "During the checkpoint process, SQL Server compares the LSN of the dirty page in buffer pool to the LSN of the data page on disk"

Paraphrase/pseudocode of second sentence:

IF LSN(data page on disk) <= LSN(dirty page in buffer pool) AND LSN(data page on disk) <= LSN(data file)

THEN Overwrite page on disk with page in buffer pool

Third sentence:

IF LSN(dirty page in buffer pool) > LSN(data page on disk) OR LSN(dirty page in buffer pool) > LSN(data file)

THEN Overwrite page in buffer pool with page on disk

The first thing I don't understand is the "=" operator in the first condition. If the LSN is equal, why overwrite anything?

Second, the only difference between the second sentence condition and the third's is the "AND LSN(data page on disk) <= LSN(data file)"

So, can someone with a better knowledge of the T-Log either explain this better or refute it? I really want to understand this properly.

Jared
CE - Microsoft

dan-572483 SSCoach Points: 15870 More actions · Answer 3

dan-572483

SSCoach

Points: 15870

May 14, 2012 at 5:15 pm

#1487452

For confirmed errors & corrections see KB968609

Jared SSC Guru Points: 61793 More actions · Answer 4

dan-572483 (5/14/2012)
For confirmed errors & corrections see KB968609

Yes, and as I said there is no mention of these 2 pages. So, if it IS correct I would like someone with a greater knowledge to explain it better if they can.

Jared
CE - Microsoft