SQL Free Buffer List

  • Hi All

    It is well documented that the Lazy Writer thread takes care of maintaining an appropriate amount of free buffers is the buffer pool, it does this by writing out dirty pages.

    My question is, if you have a system used solely for reporting (No INSERT/UPDATE/DELETES) just SELECTS. The free buffer list needs still needs to be maintained, which process removes these older clean pages from the buffer pool?

    Thanks

  • It's all managed through the buffer manager. It will remove older stuff from cache in order to support newer stuff.

    "The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
    - Theodore Roosevelt

    Author of:
    SQL Server Execution Plans
    SQL Server Query Performance Tuning

  • Grant Fritchey (1/16/2015)


    It's all managed through the buffer manager. It will remove older stuff from cache in order to support newer stuff.

    Thanks

    I found this excerpt, where does this fit into Buffer Management and the Lazy Writer?

    Can this be monitored?

    The work of scanning the buffer pool, writing dirty pages, and populating the free buffer list

    is primarily performed by the individual workers after they have scheduled an asynchronous

    read and before the read is completed. The worker gets the address of a section of the buffer

    pool containing 64 buffers from a central data structure in the SQL Server Database Engine.

    Once the read has been initiated, the worker checks to see whether the free list is too small.

    (Note that this process has consumed one or more pages of the list for its own read.) If so,

    the worker searches for buffers to free up, examining all 64 buffers, regardless of how many

    it actually finds to free up in that group of 64. If a write must be performed for a dirty buffer

    in the scanned section, the write is also scheduled.

  • There are a whole slew of performance monitor counters all dedicated to the Buffer Manager. That's the place I'd start.

    "The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
    - Theodore Roosevelt

    Author of:
    SQL Server Execution Plans
    SQL Server Query Performance Tuning

  • Thanks

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