Everything ended well - despite the warning 'do not shutdown' I powered off and powered on the VM.
This action allowed me to trigger a snapshot deletion (again) and it completed successfully.
Removing the disk of interest also completed successfully.

So, I got a happy ending.

Best Regards,
Strahil Nikolov

On Jul 7, 2019 17:41, Strahil <hunter86_bg@yahoo.com> wrote:

I think I'm getting closer.

It seems the snapshot of the VM did not get deleted and that might be the problem.

Can someone give me a hint how to remove the snapshot as I get an error:

Cannot remove Snapshot. The following disks are in ILLEGAL status: uyuni-OS-Disk1 - please remove them and try again.

Yet, removal of the disk cannot happen as I got:
Cannot detach Virtual Disk. The disk is already configured in a  snapshot. In order to detach it, remove the disk's  snapshot.

This seems like 'Catch 22' .

Best Regards,
Strahil Nikolov

On Jul 7, 2019 17:30, Strahil <hunter86_bg@yahoo.com> wrote:

Hello All,

I have changed  my system layout and the old disk is removed (echo 1 > /sys/block/sdX/device/delete)  from OS, but UI complains when I try to remove  with the following error:

Error while executing action:  Cannot remove  Virtual Disk. At least one of the VMs is not down.

Is it a limitation of oVirt ? If so, I will open an enhancement entry in bugzilla.

As far as  I remember KVM allowed me to make such stuff  without any issues so far.

Best Regards,
Strahil Nikolov