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LCK_M_U lock wait

  • February 14, 2012 at 7:54 am

    #268224

    I've got a SQL 2008 server experiencing a high percentage of LCK_M_U wait times. It's a service broker CLR Activation procedure that is the cause of this. Nothing has changed about the procedure. The CPU on the server is running 80-100% now whereas before this problem happened it was only around 30%. What can I do to relieve this waittype. Developer is looking at the code, but if no smoking gun is found there, will adding memory help alleviate?

    Thanks

  • February 14, 2012 at 8:43 am

    #1446886

    Take a look at Pinal Dave's[/url] explanation of these types of locks. This is a quick reference, but other tuning books are available that different people here like to reference.

    Jared
    CE - Microsoft

  • February 14, 2012 at 8:45 am

    #1446890

    LCK_M_U is a wait for an update lock. Something's trying to update and whatever it wants to update is locked already. Start by identifying what is causing the blocking and see if it can be optimised, then look at what is blocked and how it can be optimised.

    Chapter 6: http://www.simple-talk.com/books/sql-books/troubleshooting-sql-server-a-guide-for-the-accidental-dba/

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

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