SAN FRANCISCO — Oracle hired former Hewlett-Packard CEO Mark Hurd to help lead the database software maker in a pivotal moment in Oracle's 33-year history as it tries to muscle in on more of HP's turf.

Hurd's appointment Monday as co-president of Oracle comes a month after he resigned from HP following a sexual harassment probe.

Oracle CEO Larry Ellison loudly came to Hurd's defense at the time, calling HP's decision to oust Hurd the worst personnel decision since Apple forced out Steve Jobs — another of Ellison's friends — 25 years ago.

Oracle and HP are longtime partners, working together for 25 years to make sure their products are in sync. But Hurd's new job underscores the growing fissure between the Silicon Valley heavyweights.

Oracle is now competing in one of HP's biggest businesses — selling the computer servers that power businesses' back offices. The company said in a statement Hurd also will serve as a member of the board of directors and will report to Ellison.

Ellison praised Hurd's tenure at HP and said no other executive had more relevant experience.

"Mark did a brilliant job at HP, and I expect he'll do even better at Oracle," Ellison said. "There is no executive in the IT world with more relevant experience than Mark. Oracle's future is engineering complete and integrated hardware and software systems for the enterprise."

One of Oracle's two presidents — Charles Phillips, a former Marine and investment banker who was with the company for seven years — is resigning to make room for Hurd. The other — Safra Catz, Oracle's former chief financial officer — is staying.

Ellison said Phillips wanted to leave in December, but Ellison asked him to stay through the integration of Sun Microsystems.

Phillips was in the news earlier this year when pictures of him snuggling with his former mistress appeared on billboards around the U.S.