Thank you for your answer, however a "snapmirror release" is not working. I assume after deleting the SnapMirror relationship you also have to manually remove the snapshot, correct? I could not find that in the documentation.
Delete the Snapshot copies using the AltaVault UI or CLI and then delete the share established by the SnapMirror relationship. After Snapshot copies are deleted, the metadata is removed immediately. Freeing up data is done by asynchronous processes in the AltaVault appliance