Having done a large data migration for medical records, I would be sweating bullets doing this with presumably fluctuating transactional bank data. Out of curiosity, does anyone have recommendations for their favorite data migration tool?
I don't understand the requirement of doing the "nuclear button" migration, except maybe a shortsighted way of trying to save costs.
We generally aim to leave the old system toggled off for a release or two (allowing us to switch back in the case of a serious defect) and then rip all that old code out in the subsequent release.
I've migrated a lot of "stuff" from one place to another, from filesystems, to databases, to backups, and there is usually some perl running in the background.
Of course the scale is very different. The biggest thing I've personally migrated was in the low Tb of data. Certainly nothing so large/necessary as banking stuff.
The risk however is evaluating consistency between the systems before doing the rollback which in this case would probably require a more advanced testing capability than what was available...
[1] - https://www.oracle.com/au/middleware/technologies/goldengate...
Backups!