Oracle said Monday it planned to buy Sun for $7.4 billion, and that it was most interested in the company's Solaris OS and Java software. It said it would build soup-to-nuts systems that combine Oracle's database, middleware and applications with Sun's operating system and hardware.

"Engineering the Oracle database and the Solaris OS to work together allows us for the first time to deliver complete integrated computer systems, from database to disc," said Larry Ellison, Oracle's CEO during a conference call.