Most banks should have upgraded their legacy core banking systems 15 years ago, according to National Australia Bank CEO Cameron Clyne.However, he noted that core overhauls had proven financially unpalatable for many large financial institutions. In Australia only the Commonwealth Bank has completed its core systems revamp.Speaking after the release of the bank's half year results yesterday Clyne acknowledged that the decision to invest in a ten year technology transformation program involving a complete systems refresh, including the rollout of NAB's new core banking platform Next Gen which was developed in association with Oracle, was one of the "more difficult decisions that we made.""I would argue this is an issue that just about every commercial bank in the world faces and most of these core banking replacements should have been done 15 years ago."The reason they don't is they are long, they are complex and, of course, one generation of management enjoy  all the cost, one enjoys all the benefits - that's why you kick them down the stream and don't do them."But Clyne said he was "delighted" the bank had bitten the technology bullet even though the legacy systems in place at the bank had been "inherently stable.""We could have kicked this down the road five years and had very substantial earnings benefits over the five years. But at some point you have to bite the bullet… and if you are not doing it now all you are doing is putting the cost in down the road and it's going to be more expensive."The continued investment in technology is reflected in the bank's capitalised software balance.  For the last half year it grew to $2.22 billion, up from $1.65 billion for the similar period in 2013. As part of the technology transformation during the past six months NAB has installed the first NextGen upgrade from Oracle, which Clyne said demonstrated the benefit of partnering with a global leader rather than developing a bespoke banking solution.It also released the NAB MasterPass digital wallet, launched an online international money transfer application and installed the Oracle direct banking release which is a first step toward moving personal banking products across to the new core platform.Last month NAB also launched an upgrade of the nabConnect business banking cloud, which is hosted on its private cloud.