The process is the following :
Down Power the Controller
Move the Maintenance Link to Maintenance
Power up the Controller
As soon as you see the system led on, Remove the Link, Restore the link to maintenance mode and remove a last time.
So, to recap the link is on-off-on-off within a couple of seconds
The system led flashes quickly while erasing the database then flashes once every two secs.
If the LED does not flash rapidly then it has not been successful.