Max DOP = maximum number of concurrently *executing* threads for a single query. Not the maximum number of threads.
eg, for a query under maxdop 4, there will be a minimum of 5 threads, the 4 executing threads and a controller that's just waiting for them all to be done. There will likely be more threads that are not running.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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