Maybe the VDDK api; I am not really sure. Our backup software sends a command to vCenter to disable storage vMotion on that virtual machine while the backup is active. Once the backup has finished the software sends another command enabling storage vMotion. What I would like do to is send that "enable" command.
I just doubled checked. An unregister requires the virtual machine to be powered down.
Remove-Inventory The attempted operation cannot be performed in the current state (Powered on).