These systems have grown over the decades and each time a new one is put in the bank's IT infrastructure it has to be integrated with the others. Soon enough this becomes a maze of systems complicated enough to make the upkeep and maintenance an exceedingly difficult task.
The main problem is that these legacy systems are essential to the continued running of the banks. One anonymous developer working at a London-based North American bank says that nobody really wants to get rid of old systems as the gamble of changing them is too great.
"Even here there is another system that has meant to be retired for ages which is a front office system. I would say it will still be going in five year's time, because these systems are so heavily relied upon that to retire them is just such a big job," she says.
"A back office system is even worse because that's got every single settlement. And if that goes wrong, that is the worse thing ever as that is our system of records. It too much of a risk."
These systems are so heavily relied upon, that to retire them is too big a job.
Tom Bell, head of operation at Viewsy, used to work as an IT strategy and transformation consultant for Accenture dealing with various banks.
He agrees that banks have old and out-dated processes.
"The problems are just huge though. A few years back when I was still consulting with the banks, they still have all the old legacy systems running behind the scenes. It is such a complex problem to pick apart, it is not just a process issue, it is just expensive. And sometimes it is just easier to leave those systems running," he says.
At a London-based European bank an IT director we talked to says that he thinks "all systems are potentially ticking time bombs in a way."
"It doesn't matter how old they are, if there are faults, breakdowns will occur. It's really the severity of the faults that are the problem," he says. "What legacy systems have going for them is that the code has been around for decades so a lot of the problems within that code has been sorted out."
The real problems start when you try to integrate these old systems with new ones, he adds. "This often happens when you have to deal with new rules and regulations."
For these systems, given their complexity and the core nature of them, change is gradual.
"There is one project going on to retire a system," says our IT developer. "All these retirement projects are really, really long term because it is so much work. They can't just do it in one big bang. They have to do it gradually."
