Modules and applications have deployment descriptors—XML documents—that describe the contents of the directory or JAR file. Deployment descriptors are text documents formatted with XML tags. The J2EE specifications define a standard, portable deployment descriptors for J2EE modules and applications.
An application-specific XML-based deployment descriptor file named web.xml, which lists your application's J2EE components and their configurations as J2EE modules. Each J2EE module is a collection of one or more J2EE components of the same container type (Web or EJB) that are represented by one component deployment descriptor for that type in the web.xml file.
A WebLogic-specific deployment descriptor file named weblogic.xml, which defines how named resources in the web.xml file are mapped to WebLogic Server resources. Examples of weblogic.xml attributes include HTTP session parameters, HTTP cookie parameters, JSP parameters, resource references, security role assignments, and container attributes.
The sun hotspot JDK default is made used for development, JRockit is the one used for the production of WebLogic 11g as well as 12c. An operating system is another factor that helps in choosing the certified JDK JVM.
The usual process is that in the case of any difficulty for the manager server to get connected to any administration server at the time of start up, there is an option for the managed server to retrieve the configuration related to it from the configuration files as well as other files involved. The information thus retrieved cannot be altered and it is possible only when the administration server is really available. When the administration server is unavailable, then the managed server enters into its independence mode for carrying out its operations.
For changing the JVM can be done by following the steps below.