‘Data migrations are always difficult. It’s not just a matter of copying over some files. New and old systems will typically have completely different models for customer data, and converting between these is not straightforward. The difficulty is compounded by sheer volume (TSB have five million customers with multiple accounts) and by the fact that bank accounts are a moving target. Simply switching back to the old system would be impossible now that customers are using the new system and making transactions there. TSB attempted to handle this factor by shutting down their banking services for a whole weekend, but this evidently didn’t give them enough time to complete the migration successfully.
There are two kinds of approach to system migrations: “big bang” migrations that move all customers in one big switchover, phased migrations that move a few customers at a time (usually in progressively larger groups as confidence in the new system increases). The latter approach is typically much more difficult to design and implement, but considerably less risky and usually much easier to recover from if things go wrong. TSB appear to have taken the former approach, and are now suffering from the lack of a reliable rollback strategy, an option they would surely have taken by now if it was available to them.
There are two separate issues here: unnerving errors such as customers seeing incorrect balances or other customers’ accounts, and the capacity problems of the new system. The first issue is likely to exacerbate the latter, as people spend more time logging in to work out what’s going on with their finances. This illustrates how designing a migration such as this is not a simple technical exercise, but a complex problem that demands considering the system as a whole and the different ways in which it can fail. It’s also vital, of course, to think about the human element of these systems, since the impact on customers and branch staff is potentially catastrophic.’ – Yemi Olagbaiye, Head of Client Services, Softwire