It can take 5 to 7 minutes before all OS monitoring data is fully initialized. You may see that CPU idle is at 0.0%, which causes a Failed Critical status with OS usage. This should clear up within 5-7 minutes after adding or upgrading the OS monitoring feature to the managed server. At that point, OS monitoring data should be available for the managed server by using the show server server command. For further information, see To Add the OS Monitoring Feature in Sun N1 System Manager 1.3 Discovery and Administration Guide
Adding the base management feature to a managed server might fail due to stale or obsolete SSH entries for that managed server on the management server known_hosts file. If the add server server-name feature osmonitor agentip command fails and no true security breach has occurred, remove the entry for that managed server from the known_hosts as described in To Update the ssh_known_hosts File. Then, retry the add command.