For details, see my D0Race talk from March 14th. This is in two versions: a quick summary and a more detailed explanation.
The 4 tiers are:
D0RunII -q dist skeleton of the release
D0RunII-bin binaries, specific to a particular OS and debug+maxopt
packages source code, use fetchpkgs.sh to download
external products should download one by one using D0-glpkgs-chk.sh to
tell you what you need. However, a new script,
fetchprod.sh is now provided to do it unconditionally.
The two fetch* scripts have been in the releases since t02.08.00 and
p11.02.00 but you weren't required to use them.
----> As of t02.11.00 and p11.04.00 you will be required to use fetchpkgs.sh. This will also require a slightly different sequence of commands than you've used before. It isn't quite so simple but, we hope, it'll be more robust.
Alan