This week I worked on a messy patch. I have a RAC environment with 22.214.171.124 and an old PSU and all kind of one-off patches and I wanted to install the latest PSU (180417). It sounds simple, but it’s not so simple. The thing is that I have 4 database running from the same ORACLE_HOME, all of them are RAC, while some of them are stand-alone, some are primary for standby located on a different RAC and some are standby for a primary located on a different RAC. And the problem with that is that you cannot install a PSU on the primary first, either together or patch the standby first.