I think it is extremely hard to reason about data integrity properties in non-ACID systems.
Consider a banking application that uses linked accounts such that transactions fail if the combined balance of linked accounts is below zero. If I implement this in Oracle using Snapshot Isolation (the highest isolation level Oracle offers) in the obvious manner, I'll get silent constraint violations: transactions that should fail will succeed because MVCC can't stop two competing transactions debiting the same account pair (i.e., I have two linked accounts A & B with $100 in each and I launch two simultaneous transactions to transfer $150 away from both: afterwards, I'll end up with -$50 in both or some garbage data).
Now, you can fix if you recognise the problem in advance by doing a select-for-update or changing your schema to materialize the constraint (say by creating a linked-balance table that holds the combined balance for all pairs of linked accounts).
But it is really hard to even notice the problem, especially if you've got a few dozen tables with multiple applications writing to your database (RDBMS advocates insist that this is a good thing). And there are no automated methods for determining when this will be a problem: you just get silent data corruption or silent constraint violations in your extremely expensive "ACID-compliant" (but not really) Oracle database.
Consider a banking application that uses linked accounts such that transactions fail if the combined balance of linked accounts is below zero. If I implement this in Oracle using Snapshot Isolation (the highest isolation level Oracle offers) in the obvious manner, I'll get silent constraint violations: transactions that should fail will succeed because MVCC can't stop two competing transactions debiting the same account pair (i.e., I have two linked accounts A & B with $100 in each and I launch two simultaneous transactions to transfer $150 away from both: afterwards, I'll end up with -$50 in both or some garbage data).
Now, you can fix if you recognise the problem in advance by doing a select-for-update or changing your schema to materialize the constraint (say by creating a linked-balance table that holds the combined balance for all pairs of linked accounts).
But it is really hard to even notice the problem, especially if you've got a few dozen tables with multiple applications writing to your database (RDBMS advocates insist that this is a good thing). And there are no automated methods for determining when this will be a problem: you just get silent data corruption or silent constraint violations in your extremely expensive "ACID-compliant" (but not really) Oracle database.