Boost SQL Server Priority: A Warning for SQL Server DBA’s

Boost sql server priority is one of the processor settings that looks fairly innocuous, and could be mistaken for a turbo boost option!

Beware! It can actually cause serious problems if enabled in a production SQL Server environment.

This one I stumbled across quite by accident whilst troubleshooting cluster crashes that appeared seemingly random and without an obvious cause.

The effect of deselecting this setting (and restarting the affected instances) resulted in immediate stability of the said cluster.

What is boost sql server priority?

SQL Priority Boost is a configurable option you can set within the processor settings for a SQL instance. Doing so increases the thread priority that SQL runs at from the normal priority (7) to a much higher priority (13). Here is the link to Microsofts description of the option. By default this option is not enabled.

What are the risks of having it enabled?

The risks of having it enabled are described by Microsoft as

Raising the priority too high may drain resources from essential operating system and network functions, resulting in problems shutting down SQL Server or using other operating system tasks on the server.

In essence if you have this option selected and your SQL server instance has a big load on it, it will run at a higher priority than many other essential functions. It can bring your SQL Server to it’s knees.

How do I check my servers to see if its enabled?

In SSMS

Right click on your SQL instance, select options and then processors. You will see the option as in the picture below.

Make sure it is not selected!

boost sql server priority

Via T-SQL

The easiest way is to run this and check the value for Priority Boost.

SELECT *
FROM sys.configurations;

If you do find it enabled and decide to be sensible and disable it, you will need to restart the SQL instance to get the new configuration to take effect.

Rob StGeorge
Senior SQL Server Database Administrator residing in Auckland, NZ

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