Homa's mainframe environment runs custom-built applications that manage its supply chain. Employees can connect to it and its database via wireless devices, allowing them to immediately place product orders as they move through store aisles and warehouses.

The z9 can process 1 billion transactions per day, more than double the transaction processing capability of the zSeries z990, which Hannaford also uses. Homa said IBM also made architectural changes to the z9 that improve its ability to pull data from its database by about 30 percent.

Rapid processing capability is critical to his wireless users, but what Homa likes about the z9 is its scalability; he's using only two processors on a system that can support 64. 'This machine is doing more work than [the] other 500 servers in the data center put together,' he said.

Some users stay on mainframes because their custom-built applications are too difficult to move. But Homa is continuing with custom development by using India-based services provider Infosys Technologies Ltd. He said his software costs, including maintenance and development, are as much as 30 percent less than what he would pay if he purchased a packaged application. 'It's very easy to do custom development of our applications -- easier than buying them," he said.

While users continue to run their own mixed environments, Gartner sees an ongoing and unabated push by vendors toward utility computing, where companies buy computing power and processing power as needed, with the underlying hardware becoming less important. But that trend is "a long way from reality for most of us today," said Gartner analyst Steve Prentice.