Here are the contents of for a tweet I started.
Hard to imagine setting SQLPATH ahd glogin.sql would affect upgrade.
That’s the only changes I made.
“ORA-04023: Object SYS.STANDARD Could Not Be Validated or Authorized” during database upgrade (Doc ID 984511.1)
Documentation does not mention having customized glogin.sql and/or SQLPATH will cause upgrade to fail. Documentation has now been updated.
You can read more about Upgrade and profile scripts
AutoUpgrade validates glogin for you before starting. It looks like any improvements are only added to AutoUgrade and not traditional methods. Not only do you need to read the documentation, you also need to read again because of changes.
Lastly, here are Useful List of Examples which I find helpful.