Oracle has announced plans to offer about $220 million to acquire Portal Software, a maker of billing and revenue management software for the communications and media industry.

The database and applications company is making a cash tender offer of $4.90 per share for Portal. Subject to regulatory and other approvals, Oracle expects the transaction to close in June.

Portal's software enables communications companies to bill and manage a wide range of services including wireline and wireless phones, broadband, cable, VOIP (voice over Internet Protocol), IP television, music and video.

Oracle said it will integrate its ERP (enterprise resource planning) applications and the CRM (customer relationship management) software it acquired through the purchase of Siebel with Portal's billing and revenue management capabilities. Over time, Oracle may consider expanding use of Portal's software to other industries.

Although attention has been more heavily focused on Oracle's recent acquisitions in the open-source arena, picking up database engine vendors Sleepycat and Innobase, the company has continued steadily buying up software companies in a range of verticals - Retek in retail, i-flex in financial services and TimesTen and HotSip in the communications industry.

Oracle is also busy integrating the applications it gained through the multibillion dollar purchases of both Siebel and ERP and CRM player PeopleSoft.

Ninety-six percent or Portal’s customers use Oracle's database, while 57 percent of Portal customers already use Oracle's applications. Portal's software is in use at 240 installations in 60 countries supporting over 150 million live subscribers.

Portal's management and staff will form a global communications business unit focused on billing and revenue management. Bhaskar Gorti, Portal's senior vice president of worldwide sales, services and marketing, is set to head up the unit, with Dave Labuda, Portal's founder and chief executive officer, becoming the unit's chief technology officer.

Oracle is due to hold a conference call for customers and partners to discuss the proposed acquisition Thursday. Portal's Labuda and Gorti are due to be on the call along with Oracle President Charles Phillips.