(Republishing, or using this info in a commercial product/website, is prohibited without permission. All other uses are permitted. If in doubt, please ask.)

DAC_INIT

(Back to main page…)

Description:

This wait type is when a thread is waiting for the TDS communication protocol to initialize for the Dedicated Admin Connection (DAC) listener. The DAC is a separate connection that can be used to connect to an unresponsive server to troubleshoot and kill connections that are causing SQL Server to be unresponsive. See Books Online here for more details.

(Books Online description: “Occurs while the dedicated administrator connection is initializing.”)

Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.

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 297 in 2008 and 2008 R2, 340 in 2012, and 356 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. Initializing the TDS protocol for the DAC listener while SQL Server is starting

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

  1. SOS_Task::PostWait+9e
    EventInternal<SuspendQueueSLock>::Wait+2aa
    SOS_Task::WaitForDone+a0
    InitializeTDS+2d1
    FRunCommunicationsManager+4e
    CommunicationsManager+3c6
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+ab