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SOS_SCHEDULER_YIELD

Introduction

In overall terms this one indicates (if it is high) that there are CPU-pressure.

when a SQL Statement is being executed, then the SQL server has a mechanism so that one SQL statment does not occupy a Scheduler (think of that as a CPU. It is not correct 100%, but close to) for a very long time, so that other SQL statements cant be executed.

Therefore, after a certain amount of time (4 ms.) then the SQL statement goes of the Scheduler and are being placed in the runnable queue.

What to do

Find the most CPU intense queries and see if you can optimise them. After that, then you might consider more CPU (but why start spending money, when good DBA work can solve the problem in many cases?)

In SQL Powerhouse there is a webpart showing query costs pr. logical reads, execution time and CPU USage. this one can be used to find the expensive queries.

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