Cost Threshold For Parallelism Testing

Tim Peters shows that the Dynamics people are probably right with their assertion regarding Cost Threshold for Parallelism:

These plans are from a SQL Server 2008 R2 SP3 instance that runs a version of Microsoft Dynamics. The MS Dynamics team knows their product issues a bunch of really small queries and recommend a Max Degree of Parallelism of 1. In my case there is one query plan with a cost of 34,402 query bucks that a MAXDOP = 1 can’t afford. Increasing the MAXDOP from 1 while keeping the Cost Threshold at 5 will keep all of my little queries running in their single threaded paradise while allowing some infrequent biguns to spread their lovely wings across a few more threads. My Cost Threshold For Parallelism is set to 5 and I hope to never have to defend my settings in a dark alley with Erik Darling.

Different systems will behave in different ways, so it makes sense that they might require different settings.  In the case of Dynamics, it appears that almost all of the queries are extremely low-cost, so relatively few plans would go parallel and the ones that do, you probably want going parallel.

Related Posts

Handling MAXDOP On Azure SQL Database

Arun Sirpal plays with MAXDOP settings on Azure SQL Database: Can we change it? No. EXEC sp_configure 'cost threshold for parallelism', 10; GO RECONFIGURE; GO Msg 2812, Level 16, State 62, Line 9 Could not find stored procedure ‘sp_configure’. Msg 40510, Level 16, State 1, Line 11 Statement ‘CONFIG’ is not supported in this version of SQL Server. […]

Read More

Database Migration With dbatools

Jess Pomfret shows how easy it is to migrate databases from one SQL Server instance to another using dbatools: Now that there are no connections we can move the database.  Depending on the situation it might be worth setting the database to read only or single user mode first. In my case, I had the […]

Read More


March 2017
« Feb Apr »