[OpenIndiana-discuss] What to do when zfs destroy -f or -R or both doesn't destroy

[Harry Putnam]

Cleaning out a machine I'm about to bring down and reinstall hipster
in place of 151_9 that has been running there.

I found one stubborn snapshot that zfs destroy just will not remove.

Tried -f flag -r and -R flags

The zfs message says the snapshot is busy.

I could not find any evidence of it actually being busy and finally
rebooted just incase something was running I could not find.
On reboot I hit an important service failure that dropped me into a
console shell.

That error (although that is not what I'm asking about in this post
.. but will be, in a separate post)

Paraphrased  and shortened error message
svc:/system/filesystem/local:default failed with exit status 95
And it was put into mainenance status

Ok now back to the troublesome snapshot: In the console shell again
zfs destroy just plain will not remove this snapshot and hence the fs
itself. zfs message
ontinues to say the snapshot is busy.

Surely there is someway to get this thing destroyed?  Even if it
actually is busy.. but I doubt that is the case.