On DT3 if I try to move or copy a group with a large number of items (about 300,000 in my current example) I get a pinwheel which can persist for hours until I give up and Force Quit the application.
If I move small numbers of items, the pinwheel eventually ends with the task completed properly.
I suspect even the huge move would work if I were patient enough. It raises the questions of:
(1) Should it really take hours to do such a move? In this case the Move is of about 300,000 RSS entries which are fairly short. Should that take hour? This is on a current model iMac with 40 Gigabytes of RAM.
(2) Regardless of how much time it takes, why not have some sort of progress indicator to confirm it is working and give an ETA to completion?
FWIW the Activity Monitor shows that Devonthink 3 has maxed out my CPU at 100%. Yet there is no memory pressure at all - so it is an algorithm issue, not a RAM issue.