We realized that after a Stein -> Train upgrade of our cloud, we forgot to run "nova-manage db online_data_migrations" and did the Train -> Ussuri upgrade. We have not seen any bad side effect but where wondering if the online_data_migrations was cumulative across versions and if running it under Ussuri fixed potential changes related to Stein -> Train upgrade that we forgot to fix right after the Train upgrade. If not, are there things to do to cleanup the situation?

In your case, it’s probably fine. The real answer is “they’re cumulative until something is removed”. We “often” have online migrations that move data into new structures so we can remove the old structures later. When that happens, the online migration would be removed as well, but we have also generally accompanied that with a “blocker migration” that won’t allow dropping of the old structures if they’re not empty (i.e. because you didn’t run a migration step). I put “often” in quotes above because we haven’t had that sort of substantial change in a long time, just because things have stabilized so much. I’d have to look at your specific versions to be sure, but I think if you didn’t hit a blocker migration in the process (you’d know) then you’re fine. —-Dan