Xen Architecture

The core of the Oracle VM system is the software that runs the virtual machines. This software is the Xen virtualization system. The Xen virtualization system consists of the Xen Hypervisor and support software. Xen is a virtual machine monitor for x86, x86_64, Intel Itanium, and PowerPC architectures (Oracle only supports the x86 and x86_64 architectures). At the core of the Xen virtualization system is the Xen Hypervisor.

The Xen Hypervisor is the operating system that runs on the bare metal server. The guest OSs are on top of the Xen Hypervisor. The Xen Hypervisor, after booting, immediately loads one virtual machine: dom0. Dom0 is nothing more than a standard virtual machine but with privileges to access and control the physical hardware. Each guest runs its own operating system, independent of the Xen Hypervisor. This OS is not a further layer of a single operating system, but a distinct operating system being executed by the Xen Hypervisor. The guest OSs consist of a single dom0 guest and zero or more domU guests. In Xen terminology, a guest operating system is called a domain.