Apache Tomcat comes configured with a number of web applications, which are preconfigured in PAS for OpenEdge. Tomcat requires that there always be a ROOT application in the instance-name/webapps folder.

In PAS for OpenEdge, the default ROOT application is a deployment of oeabl.war, the OpenEdge web application. The file oeabl.war is deployed with every PAS for OpenEdge instance. You can undeploy ROOT, and deploy any valid web application in its place. The OpenEdge web application is a type of Java web application that is preconfigured with security and Java servlet interfaces that translate HTTP client requests into ABL requests, and schedules when they execute using the ABL session manager.
Note: The ROOT web application in a PAS for OpenEdge instance is the oeabl.war file deployed with the name ROOT, not the ROOT.war file for the Tomcat server. That file and other standard Tomcat configuration files and applications can be found in $CATALINA_HOME/extras.

When you create a PAS for OpenEdge instance, an OpenEdge ABL web application, oeabl.war, is automatically deployed in the instance-path/webapps/ROOT directory. The ABL web application supports all transports for an ABL application, including SOAP and REST web services, web handlers, ABL and Open Client (APSV) access. In addition, an ABL application can be represented by multiple OpenEdge ABL web applications deployed to a single PAS for OpenEdge instance.

The ROOT directory contains the manifest file for oeabl.war (in the META-INF folder), static files (in the static folder), the application definitions (in the web.xml file), and other pertinent resources such as classes, transports (APSV, REST, SOAP, and WEB), security files, and the default PROPATH folder.