Hot add CPU
Microsoft Windows uses a numeric priority system that ranges from 1 through 31 to schedule
Microsoft Windows uses a numeric priority system that ranges from 1 through 31 to schedule
threads for execution. Zero is reserved for operating system use. When several threads are
waiting to execute, Windows dispatches the thread with the highest priority.
By default, each instance of SQL Server is a priority of 7, which is referred to as the normal
priority. This default gives SQL Server threads a high enough priority to obtain sufficient CPU
resources without adversely affecting other applications.
The
priority boost
configuration option can be used to increase the priority of the threads from
an instance of SQL Server to 13. This is referred to as high priority. This setting gives SQL Server
threads a higher priority than most other applications. Thus, SQL Server threads will generally
be dispatched whenever they are ready to run and are not preempted by threads from other
applications. This can improve performance when a server is running only instances of SQL
Server and no other applications. However, if a memory-intensive operation occurs in SQL
Server, however, other applications aren’t likely to have a high-enough priority to preempt the
thread.
If you are running multiple instances of SQL Server on a computer, and turn on priority boost
for only some of the instances, the performance of any instances running at normal priority can
be adversely affected. Also, the performance of other applications and components on the
server can decline if priority boost is turned on. Therefore, it should only be used under tightly
controlled conditions.
Do not use fiber mode scheduling for routine operation. This can decrease performance
by inhibiting the regular benefits of context switching, and because some components of
cannot function correctly in fiber mode. For more information, see.
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Important
This feature will be removed in a future version of SQL Server. Avoid using this feature in
new development work, and plan to modify applications that currently use this feature.
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Important