Krieng - It seems that there isn't any limit on the number of rules you can create in OVSD. I have some 50+ test DB rules in Configuration Item. (Just for testing). The more rules you have the system performance is affected. I hope this helps
I do not believe there is a number limit but the more you have the more problems you will have in administering the rules. we have 50-100 UI & DB rules and sometimes this has made it time consuming to troubleshoot. What may be of concern to you is the number of scheduled tasks that are queued on the system as a result of rules.