Use /SP/policy HOST_AUTO_POWER_ON to power on the host when external power is applied to the server. If this policy is set to enabled, the SP sets HOST_LAST_POWER_STATE to disabled.
-> set /SP/policy HOST_AUTO_POWER_ON=value
where value can be:
enabled – When power is applied, automatically powers on the host when the SP has been booted.
disabled – Keeps the host power off when power is applied (the default).