SQL Server remote dedicated admin connection (DAC)

Category: Reliability

Item:  Remote DAC Disabled

 

What is the DAC SQL Server?

It’s a diagnostic connection for a database administrator to access SQL. The DAC can make remote troubleshooting easier when SQL Server is unresponsive. When SQL is having issues, DAC can be used to login and fix problems and avoid downtime.

 

How to identify the issue?

DAC is only allowed from a client running on the server by default. It’s a best practice to enable network connections to use it from a remote machine. You can check if the feature is enabled following the steps below:

  • Using SSMS, connect to SQL Server Instance and then right-click the Server and select FACETS  as shown below.
Figure 1 – Facets (SSMS).
  • In View Facetswindow you need to choose the Facet as “Surface Area Configuration” and then check for RemoteDacEnabled.
Figure 2 – SQL Server RemoteDacEnabled Property.

How do I enable DAC? How to fix it?

You can enable it using the interface above, just changing the property to ENABLED. Another way is to implement the change running the following script:

sp_configure 'show advanced options', 1
go
reconfigure with override
go
sp_configure 'remote admin connections', 1
go
reconfigure with override

Notes:

  • Only members of the SQL Server sysadmin role can connect using the DAC, and only one connection can be made at a time.
  • Make sure to get firewall ports opened, this will be probably port 1434, but that will vary depending on your installation.

More information

Microsoft Diagnostic Connection for Database Administrators

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