The time stamp counter of CPU on scheduler id 1 is not synchronized with other CPUs
The time stamp counter of CPU on scheduler id 1 is not synchronized with other CPUs is a warning in the SQL Server error log that seems to get a lot of interest in the forums.This warning has been explained by Microsoft, yet people seem to be confused about whether or not it is detrimental to performance, and how to stop the message from appearing. The short answer is "don't worry about it".
To provide accurate timings when you use the SET STATISTICS TIME ON statement, SQL Server 2005 is able to report figures to an accuracy of a few microseconds. It does this by using the high resolution CPU counter. For the figures to be 100% accurate it is important that all CPUs are perfectly synchronized. If the CPUs are not synchronized, and a thread moves from one CPU to another, the reported timing will be wrong. This is only an issue if you need to time your queries with this level of accuracy.
Certain power-saving technologies can cause a drift in CPU clock values. This has been a potential issue since SQL Server 2005 was released, but it has only started issuing warnings since service pack 2.
For the 99.9% of you not requiring the level of timing accuracy affected by this clock drift my advice is to ignore the warnings. It is possible to prevent them from being reported but the exact solution depends on the make and model of server. Normally it is a combination of changing a BIOS setting, and modifying the Windows Power Scheme.
If you need to rely on the accuracy of the timings, Microsoft have suggested setting the "affinity mask" option using sp_configure so that all required CPUs are selected. This prevents worker threads from moving between CPUs but I recommend setting back to the default value (0) on production servers. Please note this will guarantee accurate timings but will NOT prevent the messages from being reported.
Summary
The time stamp counter of CPU on scheduler id 1 is not synchronized with other CPUs is alarming the first time you see it as it implies all sorts of problems with your server. However, I hope this short article has put your mind at rest, and although it is annoying to see it repeated throughout the logs it is a message that can be safely ignored.Not found what you're looking for?
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