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Thread: What is the fiber mode("lightweighting pool" mode) of SQL Server?

  1. #1
    Join Date
    Mar 2005
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    What is the fiber mode("lightweighting pool" mode) of SQL Server?

    Recently I read such statments 'When SQL Server is run in "lightweight pooling" mode (fiber mode) and the DTC service is started, unexpected behavior may occur.'
    Can someone say anything about fibe mode?I am appreciated for it.

  2. #2
    Join Date
    Sep 2002
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    In EM click on properties and select processor tab and "use NT Fibres"

    is same as

    sp_configure "lightweight pooling",1
    reconfigure with override


    NT Fibres are used in high end systems.
    It is used mostly when you have 4 or more processors. There are issues using NT fibres when using MSDTC and sql mail.


    From BOL.

    lightweight pooling Option

    Use the lightweight pooling option to provide a means of reducing the system overhead associated with the excessive context switching sometimes seen in symmetric multiprocessor (SMP) environments. When excessive context switching is present, lightweight pooling may provide better throughput by performing the context switching inline, thus helping to reduce user/kernel ring transitions.

    Setting lightweight pooling to 1 causes Microsoft® SQL Server™ to switch to fiber mode scheduling. The default value for this option is 0.

    lightweight pooling is an advanced option. If you are using the sp_configure system stored procedure to change the setting, you can change lightweight pooling only when show advanced options is set to 1. The setting takes effect after stopping and restarting the server.

  3. #3
    Join Date
    Sep 2002
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    Thread Pooling (From BOL)

    SQL Server maintains a pool of operating-system threads for executing batches of SQL statements as they arrive from clients. On Microsoft Windows NT®, if the server lightweight pooling configuration option is set to 1, SQL Server maintains a pool of fibers instead of threads; fibers use fewer resources than threads. Using a pool of threads or fibers allows SQL Server to optimize the allocation of processing time when executing multiple SQL statements at the same time. The threads or fibers in this pool are known collectively as the worker threads

  4. #4
    Join Date
    Mar 2005
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    4
    thx of Mark's help.

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