The Oracle Linux 6.5 operating system (OS) image is preinstalled on the server (if ordered) in the Legacy BIOS Boot Mode. Therefore, to use the preinstalled image, you must boot the server in the Legacy BIOS Boot Mode (the default). If you boot the server in the UEFI Boot Mode, the server will not boot the Oracle Linux preinstalled image and it cannot be used. If you want to switch to UEFI Boot Mode and use Oracle Linux 6.5, you must perform a fresh installation of the Oracle Linux OS.