SQL Server Performance

Wait_Time

Discussion in 'SQL Server 2005 General DBA Questions' started by rerichards, Aug 28, 2006.

  1. rerichards New Member

    I am trying to understand the Wait_Time column in sys.dm_exec_requests.

    BOL says concerning Wait_Time: "If the request is currently blocked, this
    column returns the duration in milliseconds, of the current wait."

    In executing sys.dm_exec_requests, all my blocking_session_id's are zero, yet
    some of the Wait_Time values are non-zero. Also some of the non-zero values
    are negative.

    Please explain:
    1. If there are no requests being blocked (all blocking_session_id values are
    zero), how come there can be an non-zero value in the Wait_Time column?

    2. Since there are some non-zero values in some of the Wait_Time column, how
    can one have a negative Wait_Time?

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