Larry Ellison, the billionaire founder of the business software giant Oracle, said he intends to step down as CEO of the company today and will hand over his duties to co-presidents Mark Hurd and Safra Catz, who will serve as co-CEOs.

Ellison, who turned 70 years old last month, will remain as co-chairman and chief technology officer. Jeff Henley, Oracle’s chairman for the last 10 years, was named vice chairman.

Hurd, the former CEO of Hewlett-Packard, joined Oracle following his resignation from that company, and had essentially taken the lead on much of the day-to-day operational work. Catz has long been in charge of overseeing its financial operations.

Oracle took pains to avoid the use of the “co-CEO” title, explaining in a statement that both Hurd and Catz will be CEO, with Hurd in charge of all sales, service and the business of selling directly to industries. Catz will be in charge of all legal, financial and manufacturing. Ellison will continue to oversee all software and hardware development and engineering work.

“Safra and Mark will now report to the Oracle Board rather than to me,” Ellison said in a statement. “All the other reporting relationships will remain unchanged. The three of us have been working well together for the last several years, and we plan to continue working together for the foreseeable future. Keeping this management team in place has always been a top priority of mine.”

The news sent Oracle shares falling by more than three percent after hours.

Ellison gave few reasons behind the change, mentioning briefly on a conference call with analysts a desire to reward Hurd and Catz for their performance on the job with new titles. Given Ellison’s age, though, he may also wish to solidify the company’s leadership situation for several more years and ensure that neither Hurd nor Catz is tempted to leave. Hurd in particular has occasionally been mentioned as a candidate for other jobs.

The change atop the company came ahead of first-quarter earnings, and ahead of Oracle’s announcement of a $13 billion share buyback program. For the first quarter, Oracle reported sales of $8.6 billion up three percent. Total software plus cloud revenue rose by six percent to $6.6 billion. Cloud software sales rose 32 percent to $337 million. Earnings per share were 62 cents, up four percent year on year.

Ellison’s departure signals a changing of the guard at Oracle, but it also formalizes a division of labor that has more or less been in place since Hurd joined the company in 2010. As president, Hurd has for nearly four years been in charge of all sales operations, including the arduous task of rebuilding the battered hardware business that Oracle took on when it acquired Sun Microsystems in early 2010.

After Hurd’s ouster from HP as the result of a sexual harassment inquiry involving a female marketing exec who later recanted her story, Ellison, a personal friend, came to Hurd’s defense in public. He blasted HP’s board for making “the worst personnel decision since the idiots on the Apple board fired Steve Jobs many years ago.” He soon offered Hurd a job as Oracle’s president. Immediately he was seen as a possible successor to Ellison, though only insofar as he could work well with Catz, a quieter presence at Oracle usually heard publicly only during earnings conference calls.

The combination has largely worked. While on a quarter-by-quarter basis Oracle’s results have been uneven over the past three years, its shares have risen by about 75 percent since Hurd came on board, while revenue has risen by about 42 percent.

Usually when asked about his long-term plan for running the company, especially as his age advanced, Ellison would balk, describing his boundless energy and fiercely competitive spirit. In an hour-long interview with Kara Swisher at the 2012 edition of the D: All Things Digital conference, he disparaged rivals as varied as Salesforce.com CEO Marc Benioff and former HP CEO Léo Apotheker. “I’m fascinated by people, by what can be done with technology,” he said. “I like to test limits, the limits of the computers that we build, the limits of our company. I enjoy the competition, the process of learning. The whole thing is just fascinating. I don’t know what I would do if I retired.” And he hasn’t.