Technically speaking, the DualShield server is a Java server application running in a Java server container called Tomcat. Tomcat runs in the Java Virtual Machine (JVM), and JVM runs in the machine's Operating System such as Windows or Linux OS.
DualShield server uses a standard SQL server as its data store. By default, it includes an instance of MySQL server that's installed locally. Optionally, it can be configured to use an external SQL server that is remotely connected.
The term "DualShield Framework" is used to describe the set of software components, namely JVM, Tomcat and MySQL, that can be technically separated from the core of the DualShield server software.