Sometimes SQL Server becomes inaccessible and DBA cannot even intervene.
In such cases, there is a back door so that DBAs can find and correct what the problem is.
We call this back door DAC. In order to connect to the SQL Server with DAC, you need to configure the server after the installation.
You can find out how to configure the DAC in my article, “sp_configure (Server-Level Configurations in SQL Server)”
After making this configuration, you can click “new query” on SSMS and connect using ADMIN: clause as below.
One person can use DAC at the same time. Backup / Restore cannot be done with DAC connection.
When you try to connect in this way, you may see an error like this.
When you bypass this error, you will see that the connection has become Admin.
If you cannot connect in this way, you can use the cmd command line to connect as follows.
sqlcmd -S ServerName -U UserName -P Password -A
When you connect from the command line, you can paste the sql clauses into the command line at once and then type go and type enter.
As an example of the queries that you can run when you connect with DAC, you can find the query in my article, “How To See Current Queries On SQL Server“.