Logs show that svc:/system/sp/management:default continually restarts (see /var/log/ssm/hwmgmtd.log).
This can be due to an inability to establish an IPMI connection to the service processor.
To check IPMI connection, run the following command:
# /usr/sbin/ipmitool lan print 1
If there is no output, then the connection is down.
Power off the system, including the service processor (this could require unplugging the system). Then power on and restart the system. This should get hardware management agent working, but the problem will likely reappear.
Upgrade to the latest ILOM/Firmware package for the system. The issue is a known problem with the SPARC system firmware and its interaction with some versions of Oracle ILOM. This issue is fixed in all current firmware releases for all platforms.