Failure to calculate super-latch promotion threshold

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Failure to calculate super-latch promotion threshold

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JohnnyDBA

Posted Friday, December 28, 2012 8:29 AM

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I just checked all the servers that we've received the error from and here are the version numbers...

SQL 2012 - 11.0.3000
SQL 2008 R2 - 10.50.4000

Post #1400936

JohnGray

Posted Tuesday, January 29, 2013 1:08 PM

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Any updates to this thread? We just received this error on a SQL 2008 R2 server here in our environment.

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bluenose80

Posted Friday, February 08, 2013 2:50 AM

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I've has this message 4 times in the past month on a SQL2008 R2 server. No performance issues so it seems pretty harmless.

Post #1417543

Scott Ohar

Posted Thursday, March 07, 2013 11:26 AM

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Error msg - Failure to calculate super-latch promotion threshold - also known as Sub Latch. - Supporting article posted back in 09

http://blogs.msdn.com/b/psssql/archive/2010/03/24/how-it-works-bob-dorr-s-sql-server-i-o-presentation.aspx

Sub-latch is also referred to as super latch. These are only used for data cache page latches. They are designed to reduce the latching contention on hot pages. For example if you have a lookup table that is only a few pages in size but used by 100s of queries per second that SH latch activity is aggressive to protect the page. When SQL Server detects high rates of SH latch activity for a sustained period a buffer latch is PROMOTED to a sub-latch. A sub-latch partitions a single latch into an array of latch structures per logical CPU. In doing so the worker (always assigned to a specific CPU) only needs to acquire a SH on the sub-latch assigned to the local scheduler. This avoids interlocked activity and cache line invalidations across all physical CPUs. The acquiring of an SH sub-latch resource uses less resources and scales access to hot pages better.

Bleeding Edge - just means alot of sleepless nights

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