The snapmirror.conf no longer referred to these volumes, so its an internal state needing to be cleared.
Turns out the method that works is snapmirror release:
snapmirror release {srcpath} {dstfiler}:{dstpath}
in which {srcpath} and {dstpath} are
{volname} or {/vol/volname/qtreename}
- remove destinations
I receieved an error when I issued the command:
No release-able destination found that matches those parameters. Use 'snapmirror destinations' to see a list of release-able destinations.
But a subsequent snapmirror status revealed the Broken-off record was cleared (gone)
(Don't always believe what ONTAP tells you ! :)