Oracle Clusterware Diagnosis - Expert Oracle RAC Performance Diagnostics and Tuning - page 571

Monitoring Resource Utilization in the Cluster
Once the cluster is configured as a component of the GI and assigned a name, it's identified as such and is monitored
by the Enterprise Manager agent. Statistics are measured and collected under that name and can be viewed from the
Database Express or cloud control. The advantage of monitoring the cluster from the cloud control console is having
the ability to drill down from the O/S level to other layers of the stack, including the database.
Figure 16-5 illustrates the current O/S-level performance statistics for a 4-node cluster. As noted earlier, the CPU
usage overall across the cluster is high and needs further investigation.
Figure 16-5. Oracle 11g OEM: Cluster-level monitoring