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This wait type is when a thread is waiting for the writing out of inactive transmission objects (that track message transmissions for a dialog) to a tempdb worktable to save memory. See the Service Broker Transmission Objects section of Books Online here for more information. The thread that does this is constantly waiting, even when Service Broker is not being used.

(Books Online description: “Occurs when the Service Broker lazy flusher flushes the in-memory transmission objects to a work table.”)

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 350 in 2008 and 2008 R2, 397 in 2012, and 413 in 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 1 second every 1 second.

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

  1. Waiting for inactive transmission objects to be flushed to tempdb

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

  1. SOS_Task::PostWait+9e