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PREEMPTIVE_OS_ENCRYPTMESSAGE

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Description:

This wait type is when a thread is calling the Windows EncryptMessage 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 371 in 2008 and 2008 R2, 418 in 2012, and 434 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. Encrypting a TDS message for sending to a client (in this case, as part of a SELECT statement)
  2. Encrypting a TDS message for sending to a client (in this case, as part of processing a login request)

And many other similar call stacks.

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

  1. SOS_Task::PopWait+ba
    AutoSwitchPreemptive::~AutoSwitchPreemptive+6e
    Ssl::Encrypt+226
    CryptoBase::WriteAsync+1ae
    SNIWriteAsync+86
    TDSSNIClient::WriteAsync+164
    write_data+104
    flush_buffer+f0
    CKatmaiTds::SendRowImpl+4773
    CValOdsRow::SetDataX+3b
    CEs::GeneralEval4+fc
    CXStmtQuery::ErsqExecuteQuery+700
    CXStmtSelect::XretExecute+2dd
    CMsqlExecContext::ExecuteStmts<1,1>+375
  2. SOS_Task::PopWait+ba
    AutoSwitchPreemptive::~AutoSwitchPreemptive+6e
    Ssl::Encrypt+226
    CryptoBase::WriteAsync+1ae
    SNIWriteAsync+86
    TDSSNIClient::WriteAsync+164
    write_data+104
    intnl_flush+a1
    process_prelogin+69e
    FDoSSPIHandshake+96
    CSession::FCreateLoginRec+e0a
    process_login+6d
    process_commands+4c0
    SOS_Task::Param::Execute+12a