Those of you who blog will know that the most useful postings are the ones that you lookup yourself now and then. This one I was pulling out of my virtual class room drawer several times when asked by customers.
Quite a while ago I did a webcast about the new patching utility opatch (read the original Oracle opatch documentation for 12.2.1 here). Opatch is now used with Oracle WebLogic Server 12c but also with Oracle Fusion Middleware products such as service bus and SOA suite.
P.S. opatch is of course covered in my latest Oracle WebLogic Server 12c book.