The Portal for ArcGIS 11.2 restore fails with the error 'Failed to stop the database server' if the location of the 'db' folder differs between source and target systems.
One workaround is to set up the target system with the same location for the content directory (as specified during installation), resulting in matching 'db' folders.
If the system has already been set up, the following workflow can be used to be able to restore the backup.
Get the location for the 'db' folder from the backup by checking the file '<xxxx>-.webgissite\portal\<xxxx>-.portalsite\arcgisportal\content\items\portal\portal-config.properties'.
Create this folder on the target system.
Assign full control privileges to this folder for the account running the Portal for ArcGIS service.
Copy the original 'db' folder and its contents to the newly created location.
Log in on the portaladmin page and navigate to System > Directories > db.
Edit and enter the new path.
The Portal for ArcGIS will restart.
With the Portal for ArcGIS up and running again, restore the backup to the target system.