calculation of row size

Question

calculation of row size

MichaelJasson

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Points: 2732
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July 2, 2009 at 1:28 am

#135859

Following link gives nice information as how to calculate the row size:
http://msdn.microsoft.com/en-us/library/aa933068(SQL.80).aspx#
Although this was not told why 2 is added in row_size in following formula to calculate No of rows per page:
Number of rows per page (Rows_Per_Page) = ( 8096 ) / (Row_Size + 2)
Also the page header is not taken into consideration while calculating the no of rows per page.
Regards,
-MJ
-MJ
Please do not print mails and docx unless it is absolutely necessary. Spread environmental awareness.

Viewing 9 posts - 1 through 8 (of 8 total)

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ps. One Orange Chip Points: 29422 More actions · Answer 1

i'm not sure why they're adding 2 but it does factor page header which is 96 bytes. There is one more factor to be considered, from the end of the page starts the row numbering in reverse direction. May be this 2 is for that purpose. not sure though..

8192 bytes is the page size out of which 96 bytes is taken out for page header and remaining 8096 bytes is used for actual data.

Pradeep Singh

MichaelJasson SSCrazy Points: 2732 More actions · Answer 2

Could you please elaborate on your following comment

"There is one more factor to be considered, from the end of the page starts the row numbering in reverse direction. "

-MJ

-MJ
Please do not print mails and docx unless it is absolutely necessary. Spread environmental awareness.

ps. One Orange Chip Points: 29422 More actions · Answer 3

Row offsets for all rows present in a page are stored at the end of the page. the first offset is stored at the extreme end of the page which points towards the first record, next offset is placed before it which points to the 2nd row and so on... it keeps on increasing in reverse direction. I cant seem to find any relevent article on net as of now....

Pradeep Singh

MichaelJasson SSCrazy Points: 2732 More actions · Answer 4

Nice info. But I am worried whether this is authenticated one

-MJ

-MJ
Please do not print mails and docx unless it is absolutely necessary. Spread environmental awareness.

ps. One Orange Chip Points: 29422 More actions · Answer 5

I managed to find the link to authenticate that.:-)

http://msdn.microsoft.com/en-us/library/ms190969(SQL.90).aspx"> http://msdn.microsoft.com/en-us/library/ms190969(SQL.90).aspx

The first picture on this site explains about row offsets..

Pradeep Singh

MichaelJasson SSCrazy Points: 2732 More actions · Answer 6

This is really awesome information Praddep. Thanks for this. Don't we have any page footer as we have page header?

-MJ
Please do not print mails and docx unless it is absolutely necessary. Spread environmental awareness.

ps. One Orange Chip Points: 29422 More actions · Answer 7

We dont have a page footer as far as i know. However, i may personally consider this row offset as page footer which contains information about row offsets on the page(unless the page is an empty one)

Pradeep Singh

MANU-J. SSC-Dedicated Points: 31126 More actions · Answer 8

http://msdn.microsoft.com/en-us/library/ms178085.aspx

7.Calculate the number of rows per page (8096 free bytes per page):

Rows_Per_Page = 8096 / (Row_Size + 2)

The value 2 in the formula is for the row's entry in the slot array of the page.

HTH!

MJ