Instances are a standard Apache Tomcat feature. They allow you to create individual deployment and/or development servers that share the core Progress Application Server that you installed.
Instances are independently running copies of the core Progress Application Server. Each instance runs on its own JVM, has its own configuration with unique ports, and hosts its own web applications. However, each instance runs a Tomcat server that uses a number of common files from the same $CATALINA_HOME directory. Each instance has an alias. The default value is the directory in which the instance was created, but it can be set to some other string.
As a best practice, Progress recommends that you deploy your web applications to an instance of the Progress Application Server, rather than deploying to the Progress Application Server that you installed. This practice prevents accidental corruption of the core executables, configuration settings, and libraries. It also prevents accidental deletion of web applications if the core Progress Application Server is removed during an OpenEdge uninstall.
