The process of upgrading a Java ES deployment can involve a number of individual product upgrades performed in a particular order to ensure a smooth transition to a updated software system. Upgrades of large or complex Java ES deployments are normally carried out first in a staging environment, before being executed in a production environment. The use of a staging environment allows you to test after each product upgrade as well as to write scripts to simplify or accelerate the upgrade in a production environment.
When you have tested the upgrade process in a staging environment, and have confidence that the upgrade is working properly, you can reproduce the process in your production environment.