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This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of processing communication packets between SQL Server and clients. The SQL Server Network Interface (SNI) protocol layer is a generic framework for encapsulating TDS packets and communicating with clients over whatever protocol has been configured.
(Books Online description: “Occurs when Extended Events session buffers are flushed to targets. This wait occurs on a background thread.”)
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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 341 in 2008 and 2008 R2, 388 in 2012, and 404 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.
I have not seen this wait type be a noticeable contention point.
Known occurrences in SQL Server (list number matches call stack list):
- Flushing all buffered events to targets for a session (in this case, flushing all buffered events from a session just before changes to the session are committed)
- Flushing all buffered events to targets for a session (in this case, while flushing all events for all sessions as part of shutting down the instance)
Abbreviated call stacks (list number matches known occurrences list):
XdesRMFull::`vector deleting destructor’+14