Keep the following in mind when you boot a system:
After a SPARC based system is shut down, it is booted by using the boot command at the PROM level.
After an x86 based system is shut down, it is booted by selecting an OS instance in the GRUB menu.
In the Solaris 9 release and some Oracle Solaris 10 releases, after an x86 based system is shut down, it is booted by using the boot command at the Primary Boot Subsystem menu.
A system can be rebooted by turning the power off and then back on.
This method is not considered a clean shutdown, unless you have an x86 based system that is running a release that supports this shutdown method. See x86: Support for Using Power Button to Initiate System Shutdown. Use this shutdown method only as an alternative in emergency situations. Because system services and processes are terminated abruptly, file system damage is likely to occur. The work required to repair this type of damage could be substantial and might require the restoration of various user and system files from backup copies.
SPARC and x86 based systems use different hardware components for booting. These differences are described in Chapter 15, x86: GRUB Based Booting (Reference).