Note: This post is for ArcGIS Server 9.2 Java (any platform)
Did you ever install ArcGIS Server Java first and then go ahead and change the host name of the machine only to realize now the you will have to either re-install or run post install or contact support to fix ArcGIS Server.
Did you ever have an disk image with ArcGIS Server Java installed and configured, then you go ahead and ghost the image on many machines only to realize that all the hostnames are the same.
Don’t worry, In this post you will find information on what files has got the entries of the host name and for what purpose. This will also give you a good understanding of how ArcGIS Server Manager and Web Services Handler uses these configuration files.