Migration from Caché to IRIS can be quite a challenge if your code is grown over many years
and probably not so clean structured as you may like it. So you face the need to check your
migrated code against some reference data. A few samples might not be a problem,
but some hundred GB of data for testing might be.
A possible step could be to have your fresh code in IRIS but leave your huge datastore on Caché
and connect both environments over ECP. I have created a demo project that gives you the
opportunity to try this based on 2 Docker images with IRIS and with Caché connected over ECP.