ZfD4.01 ir4 --> ZfD6.5 upgrade. Already done schema upgrade and licensing
object creation. Next we're going to upgrade the first ZfD4 server
(nw65sp2) with inventory database (we will create the new DB from the
scratch). But, IF something goes wrong how can we roll back that server to
ZfD4 level? Basically ZEN is punch of files on SYS: volume, but does the
upgrade touch the server's registry? How about the Inventory DB rollback?

Any information appreciated,