Have you looked through the front of the DB2 V9 manuals to see what it says is changed in the release?
Can't help thinking you have to test it on V8 before going into production. If you don't, make sure you have some really important person to sign the release form, and that they are aware of this little situation. CYA.
If you are using anything non-vanilla, maybe post it here, someone might know a specific answer.