A PDomain operates like an independent server that has full hardware isolation from the other PDomain in the server. For example, you can reboot one PDomain while the other PDomain on a server continues to operate.
Each compute server is split into two partitions (two PDomains), where the bottom four CMIOU slots are part of the first partition (PDomain 0), and the top four CMIOU slots are part of the second partition (PDomain 1). Each compute server can have either two CMIOUs (quarter-populated), four CMIOUs (half-populated), or eight CMIOUs (fully-populated).
For detailed information about SuperCluster PDomains, refer to this section in the Oracle SuperCluster M8 and SuperCluster M7 Overview Guide: https://docs.oracle.com/cd/E58626_01/html/E58633/z4000d75165586.html