Acuity Lighting Group, an 11,800-employee company that sells $2 billion worth of light fixtures annually under brand names such as Lithonia and Peerless, decided to use Red Hat's Advanced Server version of the Linux operating system to run Oracle's 9i RAC database software atop a group of Dell Computer servers. The system is replacing Windows servers for running human resources and manufacturing databases, Red Hat and Acuity said Thursday at the OracleWorld conference (formerly known as Oracle OpenWorld) in San Francisco.