The Dedicated Administrator Connection

  • Comments posted here are about the content posted at http://www.sqlservercentral.com/columnists/WFillis/2786.asp


    When in doubt - test, test, test!

    Wayne

  • What do you do when you can't connect using the DAC ??

    We had a problem on a clients server recently and the CPU was flatlining. We could tell from Task Manager that SQL was the process consuming the CPU. Connecting to SQL using SQLCMD or Management Studio resulted in a rude timeout error.

    As we couldn't connect to the server, we couldn't do any diagnosis to determine the reason for the flatline.

     

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    Colt 45 - the original point and click interface

  • If you can't connect remotly, or via DAC then try locally on the server itself. If you still can't connect the only thing I can think of is to restart the SQL instance.

    Check your recompiles - use perfmon, under SQL Server: Statistics take a look at Batch Requests, Compilations and Recompilations. Compiling takes CPU, which unavoidable. Recompilations are a problem - if you are using embedded SQL try switching to stored procedures.

    Analyse master.dbo.syscacheobjects to see if objects are being dropped from the procedure cache due to memory contention.

    Also run profiler, and trace recompilations to see what code is causing recompilations (if you think that is causing your CPU).

    Another possibility for high CPU is corrupted software and drivers. I know the guys here had an old version of a Java ODBC (JDBC?) driver that caused CPU to spike. A upgrade fixed the problem. Check google.


    When in doubt - test, test, test!

    Wayne

  • DAC is available in Express, it's just disabled by default.

    http://blogs.msdn.com/sqlexpress/archive/2005/09/08/462609.aspx

    Steps to enable DAC in Express:

    1) Launch Services Applet in Control Panel

    2) Stop SQL Server Express Service

    3) Launch Properties dialog of SQL Server Express Service

    4) Add "-T7806" to the startup parameters

    5) Start the SQL Server Express service

  • Phil,

    If you can't connect, I'd contact MS immediately. You could try running SQLDiag, but that might fail as well.

  • Does anyone know if the DAC works or can be enabled in SQL 2005 Developer Edition?

    I've tried enabling Remote DAC and -T7806.  SQLCMD reports "Sqlcmd: '-A': Unexpected argument." and Management Studio simply reports reports "Dedicated administrator connections are not supported. (Object Explorer)".

    I didn't know if there might be a way to enable it.

  • You can't use DAC with Object Explorer in SSMS. You can only use a query window with DAC in Management Studio.

    Try running SQLCMD locally.

    Are you specifying servername when you run SQLCMD?


    When in doubt - test, test, test!

    Wayne

  • Thanks SSC-Enthusiastic.

    In SSMS instead of connecting to database engine directly select the new query and connect as admin:server and it connects to master in query mode.

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