In your migration file(s) you have both forward and backward steps. If operations are reducers or otherwise destructive, the forward step backs that data up to

In your migration file(s) you have both forward and backward steps. If operations are reducers or otherwise destructive, the forward step backs that data up to separate "recovery" tables. The n+1 migration may delete recovery tables. That's how I do it most of the time. Sometimes with full snapshots. Ymmv