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Description:
This wait type is a generic wait for when a thread is calling one of several Windows functions related to the registry.
(Books Online description: N/A)
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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 497 in 2008 and 2008 R2, 545 in 2012, and 561 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.
Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with the thread.
Known occurrences in SQL Server (list number matches call stack list):
- Updating the registry (in this case, noting how long SQL Server has been running)
- Updating or querying the registry (in this case, for something to do with SPNs and network configuration)
And other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PopWait+b1
SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
CServerHeartbeat::UpdateUptimeRegKey+20a
CServerHeartbeat::OnHeartbeat+49
PeriodicTimerTask::ProcessTskPkt+a
TaskReqPktTimer::ExecuteTask+63
OnDemandTaskContext::ProcessTskPkt+3e2
SystemTaskEntryPoint+426
OnDemandTaskContext::FuncEntryPoint+25
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+ab - SOS_Task::PopWait+b1
SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
SNISecAddSpn+596
TDSSNIClient::AddSPNWorker+10
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+ab