SQL Server - Cost Threshold of Parallelism

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AmitBansal Amit Bansal (Member since: 3/12/2011 4:59:54 PM)
Follow Amit at Twitter @A_Bansal : Amit Bansal is the CTO of eDominer Systems & Peopleware India. He is a consultant, trainer, writer, speaker & evangelist on SQL Server & Business Intelligence. A seasoned speaker; he speaks at major summits and conferences of Microsoft worldwide including TechED, MCT Summits, MSDN & TechNet conferences. Over the last 8 years, he has consulted, trained & mentored more than 6000 IT professionals on SQL Server & Business Intelligence and worked with top notch blue chip companies worldwide including Microsoft, Infosys, Wipro, RBS, HCL, HP, Siemens, IBM, Accenture, etc. He has delivered more than 400 workshops on SQL Server & Business Intelligence. Apart from holding many Microsoft credentials, he is also a Microsoft Most Valuable Professional (MVP) awardee on SQL Server. He is also one of the first Microsoft Certified Trainer in India. Amit has worked with Microsoft in India and US as a Subject Matter Expert in various capacities participating in OD sessions, technical reviewing, etc. He is also a very active community lead in Asia Pacific. Visit www.amitbansal.net to know more. Subscribe to Amit’s blog and be a member of his technical forum at www.SQLServerGeeks.com - an exclusive SQL Server portal. Visit www.peoplewareindia.com for Corporate Training solutions. FaceBook – http://www.facebook.com/people/Amit-Bansal/525339346 LinkedIn – http://www.linkedin.com/pub/amit-bansal/7/121/755

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Comments (4)

5/29/2012 11:07:18 AM Prashant said:

Short and simple illustration while covering up the most. Nice blog Amit!

The best explanation about estimated subtree cost I have seen so far is the below one from QP team.


Folks who want to know more can probably refer to the above link :)

Marc Jellinek
5/29/2012 11:38:57 AM Marc Jellinek said:

As per SQL Server Books Online "Configure the cost threshold for parallelism Server Configuration Option"  http://msdn.microsoft.com/en-us/library/ms190949.aspx

The cost threshold for parallelism option specifies the threshold at which SQL Server creates and runs parallel plans for queries. SQL Server creates and runs a parallel plan for a query only when the estimated cost to run a serial plan for the same query is higher than the value set in cost threshold for parallelism. The cost refers to an estimated elapsed time in seconds required to run the serial plan on a specific hardware configuration.


5/29/2012 12:55:44 PM Amit Bansal said:

Hi MArc, I knew someone would point that out :) - unfortunately there are many of those one-liners in BOL that I do not understand :( and thats why I explained in simple example using Estimated Subtree cost. However, I have updated my blog now to be a bit lenient on that BOL one-liner :)

6/3/2012 4:24:37 AM Amit Bansal said:

Thanks Prashant !


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