The US Department of Justice has finally approved Oracle's proposed acquisition of Sun Microsystems, after extending its 30-day review of the $7.4bn (£5.1bn) deal in June.

Sun stockholders approved the transaction in July, but the European Commission (EC) still needs to give its approval before the purchase can go ahead. The EC will convene on 3 September to decide whether the acquisition needs further investigation on anti-trust grounds.

Gaining US regulatory approval will be a relief for the customers of both companies. Analyst firm Gartner argued that delays in closing the deal will be unsettling for businesses wanting to buy hardware and software, because Sun's terms and conditions are likely to change if the acquisition goes through.

Oracle announced its intention to acquire Sun on 20 April, topping a bid from IBM. The database firm expects the purchase to generate more profit than the previous acquisitions of BEA, PeopleSoft and Siebel combined, and that Sun will contribute over $1.5bn (£1bn) to its non-GAAP operating profit in the first year, and more than $2bn (£1.4bn) in its second year.

Oracle uses Sun's Java software to build its Fusion Middleware, and has said that it is the most important software Oracle has attempted to acquire.