The data warehouse, developed in partnership with Sun and Accenture, will store details of the 3 billion credit and debit card transactions processed by Visa member banks every year.

Visa EU's 6000 member banks will be able to interrogate data to analyse changing spending patterns and trends in the economy in real time. Individual customer data is not identified, so consumer privacy is protected.

John Chaplin, executive vice president, Visa EU, says: "The data warehouse is pivotal to Visa's information strategy. Visa is essentially an information and technology business, and we wanted to add more value to our member banks in the European market place by offering them all this data which has always been there, but which no one has been able to easily access before."

The warehouse has been created using a combination of 6800 and 4800 Sun Fire servers, powered by UltraSparc III processors. It runs on the Solaris 8 operating system and provides 12 terrabytes of T3 storage. At peak load times, the system will be handling 20 million transactions a day.

The system was specified and integrated on behalf of Visa by consultancy Accenture.

Rob Hetherington, an Accenture financial services partner, says: "This was a complex project with a number of technology challenges including the throughput and the complexity of the data. The sheer volume of transactions is also unusually high for a data warehouse."

Visa EU says that the data warehouse may be made available to research houses and to merchants who need to know about changing spending patterns, although there are no firm plans in this area yet.