SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Performance Counters


Performance Counters

Author
Message
Robert Davis
Robert Davis
SSChampion
SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)

Group: General Forum Members
Points: 11809 Visits: 1665
Comments posted to this topic are about the item Performance Counters


My blog: SQL Soldier
SQL Server Best Practices: SQL Server Best Practices
Twitter: @SQLSoldier
My book: Pro SQL Server 2008 Mirroring
Microsoft Certified Master: SQL Server, Data Platform MVP
Database Engineer at BlueMountain Capital Management
Stewart "Arturius" Campbell
Stewart "Arturius" Campbell
One Orange Chip
One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)

Group: General Forum Members
Points: 27196 Visits: 7545
Good question.

____________________________________________
Space, the final frontier? not any more...
All limits henceforth are self-imposed.
“libera tute vulgaris ex”
Hardy21
Hardy21
SSCarpal Tunnel
SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)SSCarpal Tunnel (4.4K reputation)

Group: General Forum Members
Points: 4396 Visits: 1399
Nice question. Thanks

Thanks
vk-kirov
vk-kirov
SSCertifiable
SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)SSCertifiable (5K reputation)

Group: General Forum Members
Points: 5020 Visits: 4408
Good question, but there is a link to BOL/articles/etc missing in the explanation. Should I take the explanation on trust? :-)
free_mascot
free_mascot
SSChampion
SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)

Group: General Forum Members
Points: 12003 Visits: 2250
Good Question, Thank you!!!

---------------------------------------------------
"Thare are only 10 types of people in the world:
Those who understand binary, and those who don't."
paul.knibbs
paul.knibbs
SSCertifiable
SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)SSCertifiable (6.3K reputation)

Group: General Forum Members
Points: 6324 Visits: 6240
I had a suspicion that the obvious answer was going to be wrong, but I selected it anyway because I was curious to see what the actual answer was. One wonders why they don't call that value Pages Allocated/sec rather than Page Splits/sec!
daveb87
daveb87
Right there with Babe
Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)Right there with Babe (785 reputation)

Group: General Forum Members
Points: 785 Visits: 537
More of these types of questions please! Good way to start the day.



Robert Davis
Robert Davis
SSChampion
SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)SSChampion (11K reputation)

Group: General Forum Members
Points: 11809 Visits: 1665
It is not documented in BOL. It may be documented in some of the books on SQL Server internals. If so, I don't remember which one(s).

It is easy to prove simply set up a test where you are inserting sequential, ever-increasing data into a table so that there are no page splits, only allocations for new pages, and watch the performance counter.


My blog: SQL Soldier
SQL Server Best Practices: SQL Server Best Practices
Twitter: @SQLSoldier
My book: Pro SQL Server 2008 Mirroring
Microsoft Certified Master: SQL Server, Data Platform MVP
Database Engineer at BlueMountain Capital Management
Paul White
Paul White
SSC Guru
SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)

Group: General Forum Members
Points: 60448 Visits: 11396
Robert,

I have some (hopefully viewed as constructive) criticisms:

The observed behaviour only applies to clustered tables - heap table inserts never cause page splits. Heap inserts are not counted by the "Access MethodsTongueage Splits/sec" counter, though they do naturally affect "Access MethodsTongueages Allocated/sec".

Minimally-logged operations (even on a clustered table) do not cause "page splits" and so again only affect the 'pages allocated' counter. Taking the example of inserting into a SQL Server 2008 table clustered on a monotonically-increasing key, we observe zero page splits (but very many allocations) if the table is empty to begin with, and trace flag 610 is specified. I chose this example because it is minimally logged even under the FULL recovery model - the same behaviour applies to all other minimally-logged operations.

Adding a new page at the 'end' of the clustered index is indeed a page split: the new row is too large to fit on the last page, so it must split. Not moving any rows from the 'split' page is an optimization for this special case. Nevertheless, it explains why this operation counts as a page split.

The question explanation would have benefited from a reference - even if not officially documented. My recollection is that one of Kalen's internals books contains a reference to new page allocations in a clustered index being counted as a page split, though it does not (from memory) explain why.

The explanation given for the fourth answer option could have been worded more clearly, and again would have benefited from a reference to the internals book that explores that behaviour. QotD is useful to many people as a learning tool - so it makes sense to point them in the right direction if you can.

Paul



Paul White
SQLPerformance.com
SQLblog.com
@SQL_Kiwi
Paul White
Paul White
SSC Guru
SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)SSC Guru (60K reputation)

Group: General Forum Members
Points: 60448 Visits: 11396
paul.knibbs (9/15/2010)
One wonders why they don't call that value Pages Allocated/sec rather than Page Splits/sec!

Both counters exist, but they measure different things :-)

You may find some of the information and results in the following MSDN Best Practices article useful:
http://msdn.microsoft.com/en-us/library/cc917672.aspx



Paul White
SQLPerformance.com
SQLblog.com
@SQL_Kiwi
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum







































































































































































SQLServerCentral


Search