When the deal closes, SAP will "consolidate all cloud-related supplier assets" under the auspices of Ariba, which will operate as an independent subsidiary. Its CEO, Bob Calderoni, will be nominated to SAP's global managing board.

Those plans suggest that SAP is eager to make Ariba's substantial user base, which has other options for B2B commerce platforms, feel secure in their investments.

Ariba's network will grow to more than 1 million companies this year, SAP co-CEO Bill McDermott said during a conference call with media and analysts. "The growth opportunity in this arena is huge," he said.

SAP plans to keep Ariba's system open to other platforms, allowing customers to tap it from "any source system," according to McDermott. "All those companies that are not using SAP need not worry," he said.

Ariba's trading network and procurement applications would also complement SAP's cloud-based ERP (enterprise resource planning) suite Business ByDesign, as well as the Business One application for smaller companies, McDermott said.