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REQUEST_FOR_DEADLOCK_SEARCH

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Description:

This wait type is when the background deadlock monitor is waiting between deadlock searches. The frequency between searches is usually 5 seconds, but the interval between searches will contract and expand based on how frequently deadlocks are occurring.

(Books Online description: “Occurs while the deadlock monitor waits to start the next deadlock search. This wait is expected between deadlock detections, and lengthy total waiting time on this resource does not indicate a problem.”)

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Added in SQL Server version:

2008

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 128 in 2008 and 2008 R2, and 132 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

I have not seen this wait type be a noticeable contention point.

This wait type is one that I usually filter out as a benign wait when doing wait statistics analysis.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for something to enter the deadlock search queue

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+9e
    EventInternal<SuspendQueueSLock>::Wait+2aa
    ResQueueBase::Dequeue+1cf
    DeadlockMonitor::WorkLoop+1bb
    lockMonitor+277
    lockMonitorThread+94
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+ab