Wietse Venema writes: > I can confirm that with LMDB-0.9.10 + ITS#7756 patch, the assertion > failure goes away when I close the cursor (and its read transaction) > before changing the map or the database, and restore the cursor > afterwards. I guess this got broken when things were changed to use > external locks in order to avoid world-writable lockfiles.

Yes. Ending the read-only transaction and starting a new one means you are no longer seeing the same snapshot, though. So I hope the reason you couldn't use single transaction which I suggested previously, was

that the reader transaction needed to keep seeing the same snapshot.