SAN FRANCISCO (KCBS/AP) _ Hewlett-Packard is filing a lawsuit against former CEO Mark Hurd to prevent him from joining rival Oracle.

The complaint filed Tuesday in a California state court comes a day after Oracle hired Hurd to help lead the database software maker as it tries to muscle in on more of Hewlett-Packard’s turf.

Oracle announced the hiring of Hurd as co-president on Monday. Oracle CEO Larry Ellison came to Hurd’s defense after he resigned from Hewlett-Packard last month following a sexual harassment investigation.

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“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.”

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 that Hurd will also serve as a member of the board of directors and will report to Ellison.