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Warning: Failure to calculate super-latch promotion threshold. appears in SQL Server log

    Question

  • We are running SQL Server 2008 R2 and have just applied Service Pack 2 to our QA environment.

    Today we noticed this message in the SQL Server log:

    Warning: Failure to calculate super-latch promotion threshold.

    Can someone please tell us what this means and how to fix whatever it is?

    There is no associated error message number.

    We believe this message is new with Service Pack 2.  Can someone tell us for sure?

    This entry has occurred in the middle of the night when nothing was running that we could see and during the day.

    Environment

    SQL server 10.50.4000

    Windows Server 2008 R2 Standard Service pack 1

    Server has 4 processors, 8 Gig of Ram with 4 Gig set for SQL Server.  Usage is generally light as it is a test environment.


    KD

    Wednesday, May 08, 2013 8:35 PM

All replies

  • Hi,

    Super latch is synonymous with sub latch.  Here's more info on them : http://blogs.msdn.com/b/psssql/archive/2009/01/28/hot-it-works-sql-server-superlatch-ing-sub-latches.aspx

    As for your error, I found a couple of posts with the same error, but no resolution.  I think your best bet is to raise a connect item - http://connect.microsoft.com/SQLServer



    Thanks, Andrew

    Thursday, May 09, 2013 4:33 PM
  • Its just a warning message about super latch .

    Since SQL 2005 SuperLatches have been introducted which can enable increased performance for accessing the shared pages in the database for a multiple concurrency workload which intrun requires worker threads require SH (shared) latches. No need to set or enable any configuration this is performed automatically/dynamically based on the mutli-CPU configuration to promote a latch on a page to be a super-latch. Then this SuperLatch partitions the single latch into array of sublatch structure per CPU core.

    Super latches are way of promoting a latch for entire NUMA Node to reduce contention.

    you can also  read following detailed article 

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


    Soldier..Sir we are surrounded from all sides by enemy.. Major: Good, we can attack in any direction Thats attitude..

    Thursday, May 09, 2013 4:51 PM
    Moderator
  • Thanks for the links.  -I may try the connect forum as well.

    But I read most of this info before I posted the question.

    However, I think I need to be more specific.

    We are testing SQL Server 2008 R2 SP2 in our test environment.

    This message is appearing in the SQL Server log.  It is not clear whether this message means anything.

    Is it telling us there is an issue and SP2 is not stable?  Or is it just some warning someone forgot to take out of the code?

    Has anyone else received this message and been able to associate any other problems to it?


    KD

    Thursday, May 09, 2013 5:01 PM
  • Several people are indicating this message occured after installing SP2.  I would suggest you install the latest Cumulative Update and see if the problem is resolved.  I do not see anything listed like this, however MS is not good about publicly documenting all fixes.

    http://support.microsoft.com/kb/2730301

    Thursday, May 09, 2013 5:37 PM
    Moderator
  • Thanks, Unfortunately I really need to know for sure that this is not an issue before we upgrade our production environment.

    If I apply the patches I won't know that for certain.

    I'm hoping someone knows for sure.  That would save me a lot of time.


    KD

    Friday, May 10, 2013 2:38 PM
  • Starting from SQL server 2008 Sp1 MS has provided feature to uninstall the SP.You can go to Add remove program and uninstall SP2 , since its QA env 

    i dont think it will be much problem to you .Uninstall it and see check for the error  this is best way to check....

    Please do post what you observed.


    Soldier..Sir we are surrounded from all sides by enemy.. Major: Good, we can attack in any direction Thats attitude..

    Saturday, May 11, 2013 6:25 AM
    Moderator
  • I just noticed one of these messages today in our SQL Server log and we are at SQL2008R2 SP2 CU7...
    Thursday, April 03, 2014 1:16 PM
  • Hi,

    We did open a case with Microsoft about this.

    In our environment we continue to see this error on a couple of our test servers.

    They are quiet and unlikely to use superlatches - I think there has to be a certain number of processors for superlatches to occur.  (sorry can't remember)

    We did move SP2 to our production servers where superlatching does occur and have not seen this message.

    Microsoft indicated to us that this message is not anything to worry about.

    It's been quite awhile and we not had any issues with the test servers where this message happens.


    KD

    Thursday, April 03, 2014 1:50 PM