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Dirty Page Count Vs CleanPageCount

  • January 17, 2011 at 4:09 pm

    #149787

    I ran the script "SELECT

    (CASE WHEN ([database_id] = 32767) THEN 'Resource Database' ELSE DB_NAME (database_id) END) AS 'Database Name',

    SUM(CASE WHEN ([is_modified] = 1) THEN 1 ELSE 0 END) AS DirtyPageCount,

    SUM(CASE WHEN ([is_modified] = 1) THEN 0 ELSE 1 END) AS CleanPageCount

    FROM sys.dm_os_buffer_descriptors

    GROUP BY database_id

    ORDER BY DB_NAME(database_id)

    GO" from Paul Randal's blog. Mentioned below is the ouput

    DirtyPageCount CleanPageCount

    Db_A 4730 1974004 - 200gb

    Db_B 3251 2729686 - 300 gb

    Now the count under dirtypage in this case , are the numbers good or bad? How do we decide? Does this refer to memory pressure?Please advice.

  • January 17, 2011 at 11:05 pm

    #1274490

    Absolutely no way to tell.

    The dirty page count is just the number of pages which have been modified in cache. It's not something where there's numbers for good and bad. With no additional information there's no way to interpret those figures.

    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

  • January 18, 2011 at 7:33 am

    #1274720

    thanks

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