Doubted whether Sitecore personalization will work if DMS database downed or disabled?
Well Sitecore personalization rules will still works if it is runtime personalization.
Runtime personalization is is based on the behavior of the visitor during the current session and not based on database data.
There are a number of personalization rules that are not based on data from the database. For example, rules that depend on devices, goals, events, and traffic type to name just a few.