Ever since virtualization was invented, it has been an elusive goal to achieve the benefits of virtualization without reducing performance. Most virtualization technologies, especially hypervisors that host complete virtual machines, have overhead that prevents virtual environments from running with native performance. Virtualization can also subject applications to the "noisy neighbor" problem, in which other applications on the same host consume shared resources and cause unpredictable reduction in performance. These are obstacles to using virtualization for applications that require peak and predictable performance.
Oracle VM Server for SPARC (also called logical domains) was designed to permit zero-overhead performance. From its inception, Oracle SuperCluster was intended for the most demanding application environments, and leverages Oracle VM Server for SPARC in tuned configurations that continue to make zero-overhead, predictable virtualization a reality. See Allan Packer's article Is "Zero-Overhead Virtualization" Just Hype? for a detailed description of how Oracle SuperCluster and Oracle VM Server for SPARC achieve zero-overhead virtualization.