When i was doing that i almost forgot that we have to change to the new location for TN. To do this go to packages\WmTN\bin directory, open the setcp.bat or setcp.sh file in a text editor, and make sure the file points to the new JRE Location.
Also, keep in mind that you will have to unregister and re-register the windows services after making the changes to the server.bat, if this is on a windows box.
Add the new JRE Location to the windws PATH variable in the advanced Variables section.
Do the system requirements docs on Advantage say that 6.5 is supported running under 1.6? If you run into problems and 1.6 isn’t on the official list, tech support won’t help you. Just something to verify.