PDomains and DCUs are logical units, not physical components, that you can configure depending on how you want to isolate applications and data to satisfy particular business requirements.
These topics describe how components, particularly CMIOUs, are assigned to PDomains and DCUs, and how SPs manage system activity.
SPARC M8-8 and SPARC M7-8 Configurations and Failover Behavior (Two PDomains)
SPARC M8-8 and SPARC M7-8 Configurations and Failover Behavior (One PDomain)
For information about determining DCU assignment to a PDomain, determining CMIOU membership to a DCU, or to administer DCUs and CMIOUs, refer to the SPARC M8 and SPARC M7 Servers Administration Guide.