Red Hat Enterprise Linux for x86-64 provides installation media for an i686 hardware platform. The installation media of Red Hat Enterprise Linux for x86-64 contain both the Red Hat Enterprise Linux and Red Hat Enterprise Linux Atomic packages. The Atomic component enables free software users to deploy atomic updates at the OS level in a few simple steps without rebooting their systems. This process of atomic update is often provided by Red Hat Enterprise Linux Atomic subscription services to enterprises.
Oracle Linux Advanced Server provides the ability to install on the x86-64 hardware, and Xen guests on this. The instruction, configuration and documentation you see for Oracle Linux Advanced Server is applies to the Oracle Linux Advanced Server for x86-64, not the Oracle Linux Advanced Server for i686. It is the same operating environment, simply differing hardware architectures.
Oracle Linux Advanced Server 9.0 is the current version of Oracle Linux. Oracle Linux Advanced Server 9.0 provides crash consistency between the host and the guest operating systems. The game of crash consistency between the host OS and guest OS is a challenge for the host OS and the guest OS. If the host OS crashes, the guest OS crashes also. Another challenge is that the host OS and the guest OS may use the same memory ranges. If the host OS writes to a page, the guest OS may also use that page. If the host OS writes that page as dirty, then the guest OS should also mark the page as dirty. Oracle Linux Advanced Server 9.0 handles this scenario in crash consistency. A memory bit or bit mask is used to mark the page as dirty, then only the host OS writes to the page. The guest OS may use the page, but it will not see any dirty bits.
Oracle Linux Advanced Server 4.8 provides BIOS level virtualization. In a Xen virtual environment, an OS is executing on the hardware in a virtual box. This way, the OS doesn't have to share resources with other operating systems on the hardware, while in native mode, the OS is sharing resources with other operating systems on the hardware, rather than running in a virtual guest on the host OS. 7211a4ac4a