Now that some folks are upgrading to version 12.3.1, we've seen a couple of upgrade issues. There are a couple of issues that I've seen questions about which I can give you a solution for:
"When I try to upgrade to 12.3.1 on an S11 system, I get an error saying 'The configured Oracle Solaris 11
publisher, <publisher>, does not support the version of Oracle Solaris 11 that is
installed on this system.' What do I do?"
The Oracle Solaris 11 publisher for your environment needs to include the full version of S11 that you're using. You can solve this problem by updating your repository.
"How much disk space do I need to have free for an upgrade?"
This will depend on your environment to some extent, but 100 GB is a good guideline.