We had to change several of our database enviromental variables. We had tuned them down below the default settings and the installtion program assumes they are minimally at default. Here is a list of the variables that bit us:
sortheap
logfilsiz
buffpage
logsecond
stmtheap
locklist
Theses variables had to be increased so the individualy databases could be migrated.
Out of 3 inplace upgrades we only really had a problem with upgrade. The instance failed to upgrade on our production server. We had to drop it and recreate the instance. Then I had to recatalog the databases.
I would highly recommend that you get a snapshot of all your instance and databases variables, along with system environmental variables.
We upgraded from ver 7 fixpak 9 or 12 to ver 8 fixpak 3 for Windows.