PREEMPTIVE_OS_ACCEPTSECURITYCONTEXT

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Description:

This wait type is a generic wait for when a thread is calling the Windows AcceptSecurityContext function.

(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 366 in 2008 and 2008 R2, 413 in 2012, and 429 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:

If you see long waits for this wait type, have your infrastructure team investigate performance issues with servers that provide security authentication and authorization, such as Active Directory Controllers and Domain Controllers.

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):

1. Establishing a security context (in this case, as part of dispatching a Service Broker message)

And other similar call stacks.

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

1. SOS_Task::PopWait+ba
   AutoSwitchPreemptive::~AutoSwitchPreemptive+6e
   CSbSSPIAuthenticator::VerifyForAccept+17b
   CSbSSPICommon::InputData+47
   CSbEndpointState::ProcessSSPIData+2b
   CSbEndpointState::VerifySSPI+34d
   CSbEndpointState::ExecuteAction+55
   CSbEndpointState::TriggerEvent+29d
   CSbEndpointState::DispatchMessage+440
   CConnectionEndpoint::DispatchCurrentMsg+25
   CConnectionEndpoint::DelimitOneRecvMessage+16b
   CConnectionEndpoint::ReceiveTask_IdempotentInvoke+4b6
   CConnectionReceiveTask::IdempotentInvoke+15
   CSbTaskManager::HandleReusableTask+247