PREEMPTIVE_SP_SERVER_DIAGNOSTICS

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Description:

This wait type is when a background thread is running the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. You can read more about it:

• In Books Online, here
• On the PSS blog (long, detailed post) here

(Books Online description: N/A)

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Added in SQL Server version:

2012

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 735 in 2012 and 753 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. Running the sp_server_diagnostics procedure

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

1. SOS_Task::PushWait+105
   SOS_ExternalAutoWait::SOS_ExternalAutoWait+9e
   AutoSwitchPreemptive::AutoSwitchPreemptive+27
   DiagnoseComponentMgr::Execute+15b
   SystemHealthMonitor+12b
   SystemHealthMonitorThread+94
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab