I'm in the OP's corner.
In light of today's data-mining and AI volumes of data - anyone saying this is hard or costly for ANZ is living in yesterday.
I've been paid to collect and store data since paper and mag-tape days.
I've built databases for a living for a decade or two.
Let's look at the data volume involved.
Lets say 2 million accounts with 10 transactions a day and 1000 characters per transaction.
That's 7 TB per year.
10 years of data on 3 disks for a total of 3000 $NZ.
You can tweak those inputs to give every soul in NZ 2 accounts, 100 transactions per day...
Whoopee - that's 150 TB & just silly - and it's still not going to frighten anyone.
If much of it sits in slower-access storage - so be it.
As a customer is logging-in, pull it up into working storage.
Hey, it's 2024, this is isn't financially or technically difficult - we just don't expect our banks to give us very much in return for what they cost us.