Secret passages and skipped meals: Oracle's CEO gave us a rare peek at what it really takes to run a $37 billion company

With $37 billion in annual revenue, Oracle is one of the world's biggest tech companies. And every year tens of thousands of customers, partners, industry analysts, and journalists descend upon San Francisco for the company's annual OpenWorld tech conference.

It is a pinnacle week for the company's top execs, its two famous CEOs, Safra Catz and Mark Hurd, and its even more famous founder, Larry Ellison, who stepped down from the CEO role in 2014 to become executive chairman and CTO, though he's still very much the leader of the executive triad.

Oracle invited me to spend a full day shadowing Hurd last week at OpenWorld, as he met with customers, analysts and others on the biggest day of the conference.

During the week, Hurd met with nearly 500 people either in individual 1:1 meetings or in small groups, answering their questions, solving problems, issuing reassurances and explaining the company's plans and strategy, all at a surprisingly exhausting pace.

It was a rare close-up look at the hard work a CEO really does to run global tech company.