But the manufacturers can rest easy no longer: it now seems that large-scale OLTP systems can be run on networked PCs. The evidence for this comes from Richmond Savings Credit Union, a Canadian bank with the largest PC-based OLTP network in the world.
Instead of a mainframe in a giant air- conditioned computer centre, Richmond simply has a dozen or so PCs strung together in a tiny back office. The system handles 100,000 transactions a day for 250,000 accounts spread over 350 PC workstations throughout the branch network. It also deals with mortgage processing and statements and has on-line links to credit-card operators and credit bureaus.
Although small by UK banking standards, Richmond ranks by size in the top 10 per cent of all North American financial institutions. And Prologic, the Canadian software house that created the system, insists that scaling up is simply a matter of adding more PCs.
The seeds of the system were sown in 1984, when a group of computer specialists became enthusiastic about the growing power of PCs. This could be the future of computing, they decided - but only with a specialised downsizing language.
They formed Prologic to develop the 'Probe' language and then came across Richmond Savings, a struggling company at the time and hampered by an inflexible mainframe system. There was a shared vision of the future, said Allen Lacroix, the bank's vice-president in charge of technology and operations support. 'We all felt very positive about what PCs could ultimately do, rather than what they were doing then.'
Entrusting the bank's future to a fledgling software house was a risk, but Richmond proceeded. The first phase, Mr Lacroix explained, was to build a 'decision support' link between the bank's mainframe and branch PCs. 'At last, we started to understand the behaviour of our customers,' he said. Among other things, the system identified which types of customers were buying which products, and provided 'what if' analyses to gauge the possible effects of changes in charging policy.
The second phase replaced the mainframe's slave terminals with PCs, which could communicate with the central computer but also run spreadsheet and word-processing programs.
The final phase, completed in 1987, introduced a fully functional banking transaction system, again written in the Probe language. Use of 'client / server' technology enables processing work to be shared between workstations and the host PCs at head office. Response time averages two seconds.
Accounts can be opened, deposits and withdrawals made, and up-to-the-minute marketing and creditworthiness information obtained at the same PC. Processing mortgage applications now takes minutes, not days. Better-informed lending decisions have produced a sharp fall in the level of bad debts.
Probe enabled Richmond to develop the system it wanted in a fraction of the time it would have taken using conventional means.
With traditional mainframe languages, a banking system typically requires up to 50 man-years to develop; Richmond's took 21 man-months. Instead of 2 million lines of program code, it has less than 50,000.
It is also highly flexible. Richmond can now react far faster to market conditions, making about two software changes per working day to the system. Previously, it was limited to about five changes a month.
Mr Lacroix also pointed out that the bank had made significant savings - despite having to bear the cost of developing the system in the first place. It no longer has a mainframe, just ordinary PCs purchased by mail order. 'We didn't set out to save money, but we have anyway,' he said.
Other banks have realised the potential; more than 100 financial institutions worldwide have switched to the system, now separately marketed by Prologic alongside its Probe language.
Bristol-based Apak Systems markets it in the UK - although its director, Ray Moy, conceded it is sometimes an uphill struggle to persuade conservative UK institutions that OLTP downsizing on this scale is possible. 'It's still difficult to convince people that several hundred workstations can link up to a single PC,' he said.
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