Oracle said that its $7.4 billion (£4.5 billion) purchase of Sun Microsystems has been completed.
The closing of the all-cash deal comes one week after the European Union gave its long-awaited approval, saying the combined company will not significantly affect competition in its markets.
Business software developer Oracle said it was buying Sun, a struggling computer server and software maker, last April. The US Department Justice cleared the acquisition four months later.
The deal gives Oracle ownership of the Java programming language, which runs on more than a billion devices, and the Solaris operating system.
Sun, was a dot-com highflyer that advanced the technology used to link computers, making them more useful as a network.