Description:
As per article from https://docs.microsoft.com/en-us/windows-server/identity/ad-fs/design/federation-server-farm-using-sql-server, we need to run the following command to update the SQL connection string for the AD FS configuration database:
PS:\>$temp.put()
The update is necessary to support SQL Always On feature.
However, there's an "exception error" when you run the above script in PowerShell.
Resolution:
For modifying the connection string on the additional ADFS server in the Farm, you need to stop the ADFS Service first. After that run the above script and start the ADFS Service again.