SAP AG, largest maker of enterprise-applications software, agreed to buy Ariba Inc. for $4.3 billion in the German company's second multi-billion purchase in cloud computing to take on Oracle Corp.

SAP will pay $45 a share, or 20 percent more than Ariba's May 21 closing price, Walldorf, Germany-based SAP said yesterday. The transaction, subject to approval by Ariba shareholders and regulators, will probably be completed by the end of August, SAP Chief Financial Officer Werner Brandt said on a conference call.

Ariba is the leader in cloud-based collaborative commerce applications, counting BHP Billiton Ltd. and Deutsche Bank AG among customers it connects to more than 730,000 suppliers. As competition in on-demand software intensifies, SAP has increased its pace of acquisitions, last buying SuccessFactors Inc. in December. With businesses increasingly choosing to store and process data on the Web, SAP is shifting many of its staple applications to the Internet.