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Description:
This wait type is when a thread is waiting for a new SNI listener to be created after a NUMA node becomes available for us. 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 there is a wait for all tasks to finish during a NUMA node state change.”)
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Added in SQL Server version:
2008
Removed in SQL Server version:
N/A
Extended Events wait_type value:
Maps to the SNI_WAIT_TASK_FINISH map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here).
The map_key value in sys.dm_xe_map_values is 292 in 2008 and 2008 R2, 335 in 2012, and 351 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.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for a new SNI listener to be created
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+9e
EventInternal<SuspendQueueSLock>::Wait+2aa
SOS_Task::WaitForDone+a0
NodeListener::Initialize+343
SNIStartListening+7e
TDSSNIClient::Init+230
InitializeTDS+61
FRunCommunicationsManager+4e
CommunicationsManager+3c6
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+ab