PREEMPTIVE_OS_CRYPTACQUIRECONTEXT

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Description:

This wait type is when a thread is calling the Windows CryptAcquireContext 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 421 in 2008 and 2008 R2, 469 in 2012, and 485 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 cryptographic services to the domain (for instance, the server for an Enterprise Key Management system).

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. Retrieving certificate information (in this case, while checking the database certificates during instance startup)
2. Retrieving asymmetric key information (in this case, while decrypting a column)
3. Retrieving security information (in this case, while changing row level security as part of an ALTER TABLE column)

And other similar stacks.

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

1. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+5d
   CSECCryptoContext::Init+330
   CSECSessionCryptoContext::GetCryptoContext+c0
   GetCertDerivedAttributesFromBytes+85
   CMEDCatObfusKey::GetCMEDCertificate+7e9
   CMEDCacheEntryFactory::FindOrCreateCacheEntry+196
   CMEDCacheEntryFactory::GetProxiedCacheEntryById+f6
   CMEDProxyDatabase::GetCertificateById+6c
   SynchronizeSystemCertificates+be
   StartUp::StartResourceDB+6df
   StartUp::StartModelAndTempdb+3ae
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab
2. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+5d
   CSECCryptoContext::Init+330
   CSECSessionCryptoContext::GetCryptoContext+c0
   GetAsymKeyProperty+a3
   SsvarAsymKeyPropI4Wstr+235
   CEsExec::GeneralEval4+e7
   CQScanFilterNew::GetRowHelper+55
   CQScanNLJoinNew::GetRowHelper+4f
   CQScanNLJoinNew::GetRowHelper+4f
   CQScanNLJoinNew::GetRowHelper+f4
   CQScanNLJoinNew::GetRowHelper+4f
   CQScanNLJoinNew::GetRowHelper+4f
   CQueryScan::GetRow+81
   CXStmtQuery::ErsqExecuteQuery+36d
   CXStmtSelect::XretExecute+2e7
   CMsqlExecContext::ExecuteStmts<1,1>+427
   CMsqlExecContext::FExecute+a43
   CSQLSource::Execute+86c
   process_request+a57
   process_commands+4a3
3. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+5d
   CSECCryptoContext::Init+330
   CSECSessionCryptoContext::GetCryptoContext+c0
   ISECCryptoServices::Get+87
   CStmtAlterTable::XretExecute+2712
   CMsqlExecContext::ExecuteStmts<1,1>+427
   CMsqlExecContext::FExecute+a43
   CSQLSource::Execute+86c
   process_request+a57
   process_commands+4a3
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab