Three years ago, business software maker Oracle acquired Micros, a hotel and restaurant technology company, for $5.3 billion in cash. Micros was the market leader. More hotels used Micros’s software to check in and check out guests than any other company’s reservation management software. For more than two decades its servers hummed under the front desks and in the back offices at tens of thousands of properties worldwide. One of the knocks against Micros’ hotel software was that it was antiquated. One hotelier called it “a DOS pig with lipstick,” referring to the 1980s Microsoft disk operating system for computers.