The installer performs some dependency and compatibility checking. Can only check what is installed locally. For example, if your solution is using a remote Directory Server instance, the installer cannot check whether the remote Directory Server is compatible with the Access Manager you are installing. If you are installing and configuring an all-new solution. It might be an issue if you are adding a new component to an established solution, or building a Sun Java System around existing components. For example, if you are already using Directory Server, and you are building a solution using Access Manager, Messaging Server, Calendar Server, and Communications Express around the existing Directory Server, compatibility among the components becomes an issue.
Component Dependency Checking. The Java ES installer will prevent you from omitting components that are required by other components you have selected for installation, but only on the local host. In a distributed solution, the installer does not check the remote host to verify that the remote component is there. You are responsible for verifying that the remote component is compatible and in the proper running state.
Upgrading. The Java ES installer does not perform any component upgrading except when Application Server and Message Queue have already been installed with the Solaris OS. In this case, the installer asks if you want to upgrade Application Server and Message Queue during installation.
The Java ES installer does perform upgrade of shared components. For more information of this topic, see Surveying Existing Hosts in Sun Java Enterprise System 2005Q4 Installation Guide for UNIX.