When PDomains are powered on, their clocks synchronize to the NTP server when the system is configured to listen to NTP multicast (the default for the current Oracle Solaris OS). If the PDomains and SPs use the same NTP server, events logged in the Oracle Solaris OS and on the SP can be correlated based on their time stamps. If the PDomains and SPs use different NTP servers, their times might drift, and correlating log files could become difficult. If you connect a domain to an NTP server other than the one used by the SP, ensure that both are low-stratum NTP servers that provide the same degree of accuracy.
Oracle ILOM Administrator's Guide for Configuration and Maintenance