If you give 9vx a full Plan 9 distribution, you can use pull to update it just like any other distribution. Early copies of 9vx had a /dist/replica/client/plan9.db but it didn't match all the files I'd deleted to cut the size of the archive down. In 0.12 I deleted the plan9.db too, so that pull wouldn't try to run.
If you want to run pull, you should start with a full tree. I have posted one at http://pdos.csail.mit.edu/~rsc/plan9.tar.bz2 You should be able to run pull successfully if you use that tree as your root. You can also start with a stock Plan 9 CD, if you know how to extract it into your local file system, but you will need to populate /dist/replica/client appropriately and also copy /dist/replica/network from a 9vx tree, since I haven't gotten those changes back into the distribution yet. Russ
