An initial installation overwrites the system's disk with the new version of the Solaris OS. If your system is not running the Solaris OS, you must perform an initial installation.
If the system is already running the Solaris OS, you can choose to perform an initial installation. If you want to preserve any local modifications, before you install, you must back up the local modifications. After you complete the installation, you can restore the local modifications.
You can use any of the Solaris installation methods to perform an initial installation. For detailed information about the different Solaris installation methods, refer to Choosing a Solaris Installation Method.