Where I can find out who has disabled monitoring of specific connection in my diagnostic server ? is there a way ?
There is a way to find that out.
In the directory {DS dir}\Agent\log is a file called config-audit.log. In this file search for this string
<ADK.Type>1200</ADK.Type>
Immediately below that will be some lines like this:
<ADK.Property name="enabled">False</ADK.Property>
<ADK.Property name="name">ConnectionName</ADK.Property>
The XML element with the name attribute contains the name of the connection that was enabled or disabled. This name will be in the internal format which has any backslashes replaced by underscores and _sqlserver appended for SQL Server connections. For example hostname_instancename_sqlserver or hostname_ sqlserver for a default instance or hostname for a Windows connection.
Just above the text that was searched for will be a line like this that show shows the user who made the change and the host they were using
05 Apr 2013 12:48:04,246 DEBUG [MessageListenerNotifier(Job#11269)] User: Domain\User (ADMIN) at 99_99_99_99/55288 (hostname)
