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FFT_NSO_DB_LIST

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Description:

This wait type is when a thread is waiting for access to the list of databases maintained by the Filetable subsystem.

(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 816 in 2012 and 835 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. Waiting for access to the Filetable database list (in this case, while shutting down a database that has AUTO_CLOSE enabled)
  2. Waiting for access to the Filetable database list (in this case, while shutting down a database that has AUTO_CLOSE enabled)

And other similar call stacks.

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

  1. SOS_Task::PostWait+9e
    EventInternal<SuspendQueueSLock>::Wait+2ca
    SOS_RWLock::GetLongWait+10b
    SOS_RWLock::GetLock+14b
    FFtNso::NotifyDbAutoClose+127
    FFtSql::NotifyDbAutoClose+39
    TaskDatabaseAutoClose::ProcessTskPkt+373
    OnDemandTaskContext::ProcessTskPkt+3e2
    SystemTaskEntryPoint+426
    OnDemandTaskContext::FuncEntryPoint+25
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+ab
  2. SOS_Task::PostWait+9e
    EventInternal<SuspendQueueSLock>::Wait+2ca
    SOS_RWLock::GetLongWait+10b
    SOS_RWLock::GetLock+14b
    FFtNso::UnregisterDatabase+167
    FFtSqlStore::ShutdownDatabase+b3
    DBMgr::ShutdownDB+200
    DBMgr::CleanShutdownDB+51c
    TaskDatabaseAutoClose::ProcessTskPkt+386
    OnDemandTaskContext::ProcessTskPkt+3e2
    SystemTaskEntryPoint+426
    OnDemandTaskContext::FuncEntryPoint+25
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+ab