the solution/trick was to use the version 188.8.131.52 of the 3dm2 tool, which seems to be the last version without need of JRE. You should download it from http://www.3ware.com/support/downloadpage.asp.
After untar’ing it you need to change an line in the file “install.3dm”:
Original: cat /etc/redhat-release | grep -i ‘hat’ > /dev/null
New/Replace: cat /etc/redhat-release | grep -i ‘xenserver’ > /dev/null
Now you can execute that file:
# ./install.3dm -i
Handy tip to install the 3DM2 web gui on XenServer