"it gets tricky when you have multiple older platforms running in ways which are business critical and so there's a high risk of disruption in any move. With legacy IT over decades it's a nightmare of different coding and operating systems."
Mrs A manged the transfer of a vast set of data bases etc from a household name in the UK to the USA 10+ years ago . It was a nightmare - every time they started the move (which had to be done over long weekends as it was active in normal business hours) they found another "legacy" - some dating back to the late 1950's - chugging away below layers of new code. Planned at 3 months, actually took 30. One issue was identifying all the various data base entries for the same person under filed under different codes - Asturias56, 56ASturias, Snr Asturias, Mr & Mrs Asturias - and that's before you get to addresses and then different products and accounts.........