Whenever we are going to apply a patch or a patch set update (PSU), the traditional procedure involves stopping all processes running on the Oracle home directory involved, which forces us to stop providing service to start the patching, a process that although it is relatively easy and simple, is subject to eventual failures that, if they occur, can lead to a crisis situation in which the DBA must identify the problem and try to solve it, or choose to rollback.
In this article I have published in Oracle Technology Network I explain how to do it, enjoy the reading!