update: Software maker Oracle said Monday it will acquire rival Siebel Systems in a deal worth $5.8 billion, marking the second major competitor the company has targeted since mid-2004. Oracle executives said the mega-deal is intended as a "major beachhead" against archrival SAP, which is the world's largest business-applications seller. Siebel specializes in customer relationship management (CRM) software. Oracle said the Siebel acquisition will add 4,000 customers and 3.4 million CRM users. Oracle Chief Executive Larry Ellison said the deal was in part fueled by requests from partners and customers, such as General Electric, that wanted to hold a single...