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This wait type is when a Service Broker transmission queue is empty and the two internal transmitter threads are waiting for work to do.

(Books Online description: “Occurs when the Service Broker transmitter is waiting for work.”)

Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.

Added in SQL Server version:


Removed in SQL Server version:


Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 169 in 2008 and 2008 R2, and 173 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. The wait time for this wait type will increase by 2 seconds every 1 second when Service Broker is not being used.

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

  1. Waiting for work for a transmission queue

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

  1. SOS_Task::PostWait+90