Live Upgrade guidelines
Hello
This doc explain a bit the guidelines to do LU (Live Upgrade)
If you are going to patch / upgrade the system running ZFS root or SVM the best and safe way is LU (Live ugprade).
Before doing an upgrade or install patches you have to check the system FW as well to avoid know issues that could leave the system unbootable.
If the FW is very old please upgrade the Firmware first. To check the FW for your system use the handbook: https://support.oracle.com/handbook_private/index.html
or in this link Firmware Releases
See these docs with a lot of information about LU: