. https://blog.pythian.com/upgrade-oracle-gi-to-18c/
blog article
Now that Oracle Grid Infrastructure (GI) 19c has been released, it is time to upgrade your GI to 18c! I am presenting here a well-tested procedure to upgrade your Grid Infrastructure to 18c. It has been designed and applied on many Exadatas and the procedure can also be applied on non-Exadata systems. You will notice that it is very close to upgrade your Grid Infrastructure to 12c. It is not a secret to anyone, Oracle’s version naming has always been changed in a not-really-consistent manner across the years making it not really easy to follow. Then this new style of yearly release also came with its new version numbering. Indeed, we used to name our directories with the version number like and then create a new directory like when we would perform an out-of-place upgrade to a new major version. Nowadays, even if 18c is actually version, the database came with an 18.1 version and GI came with an 18.0 version. Each RU will increment the second number of the version: January 19 RU (patch 28828717) being GI version 18.5, and so on. READ MORE