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SNI_CRITICAL_SECTION

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Description:

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 during internal synchronization within SQL Server networking components.”)

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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 276 in 2008 and 2008 R2, 283 in 2012, and 290 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):

  1. Shutting down the current connection
  2. Completing a read on the current connection

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

  1. SOS_Task::PostWait+9e
    SOS_UnfairRecursiveMutexExtendedGuarantee::LongWait+201
    CCriticalSectionSOS::Enter+177
    SNIGetInfo+52f
    ConnectivityTraceManager::InsertTraceRecord+263
    CNetConnection::TraceConnClose+17e
    kill_session+36
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8
  2. SOS_Task::PostWait+90
    SOS_UnfairRecursiveMutexExtendedGuarantee::LongWait+1ff
    CCriticalSectionSOS::Enter+177
    CryptoBase::ReadDone+132
    SNIReadDone+ac
    SOS_Node::ListenOnIOCompletionPort+2e9
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8