I.B.M. is introducing on Tuesday a new line of mainframe computers, adding yet another chapter to a remarkable story of technological longevity and business strategy.

The new model, the zEnterprise EC12, has strengthened the traditional mainframe’s skill of reliably and securely handling vast volumes of transactions. That is why the mainframe is still the digital workhorse for banking and telecommunications networks — and why mainframes are selling briskly in the emerging economies of Asia and Africa.

The new models have added capabilities for computing chores that are growing rapidly, like analyzing torrents of data from the Web and corporate databases to predict consumer behavior and business risks. Name a trend in corporate computing — cloud computing, data center consolidation, flash-memory storage, so-called green computing — and I.B.M. executives point to tailored features in its mainframe that deliver the goods.

The death of the mainframe has been predicted many times over the years. But it has prevailed because it has been overhauled time and again. In the early 1990s, the personal computer revolution took off and I.B.M., wedded to its big-iron computers, was in deep trouble. To make the mainframe more competitive, its insides were retooled, using low-cost microprocessors as the computing engine.