Installing the Solaris 10 Software
You'll perform an initial installation either on a system that does not have an existing Solaris operating system already installed on it or when you want to completely wipe out the existing operating system and reinstall it.
An upgrade is performed on a system that is already running Solaris 7, Solaris 8, Solaris 9, or a previous release of Solaris 10. An upgrade will save as many modifications as possible from the previous version of Solaris that is currently running on your system.
Upgrading to a New Software Group You cannot upgrade your system to a software group that is not currently installed on the system. For example, you cannot upgrade to the Developer Solaris Software group if you previously installed the End User Solaris Software group. You can, however, add software that is not currently part of the installed software group to a system.
Another option when upgrading your system is to take advantage of the Solaris live upgrade, which enables an upgrade to be installed while the operating system is running and can significantly reduce the downtime associated with an upgrade. The process involves creating a duplicate boot environment on an unused disk slice and upgrading the duplicate boot environment. When you're ready to switch and make the upgraded boot environment active, you simply activate it and reboot. The old boot environment remains available as a fallback to the original boot environment and allows you to quickly reactivate and reboot the old environment. This is useful if you need to back out of the upgrade and go back to the previous operating system release.
Regardless of whether you are going to perform an initial installation or an upgrade, you need to first determine whether your hardware meets the minimum requirements to support the Solaris 10 environment.