If you use the Oracle VM Server software that is preinstalled on your system, you must ensure that it is compatible with the version of Oracle VM Manager that you use to manage your Oracle VM infrastructure. If necessary, upgrade your Oracle VM Server or Oracle VM Manager so that both are at the same version.
For information about upgrading the Oracle VM software, see the Oracle VM Installation and Upgrade Guide at the: http://docs.oracle.com/cd/E50245_01/index.html