i am very confused about use of db or persistent store, if i use db then i have to store it on mmc because i have read some where that all BB devices do not allow to store db in phone memory, if i make db on mmc then user can delete it, and the second approach is Persistent Store, but it is not easy to manipulate when we have large amount of data, how can manage tons of keys to retrieve and store data in persistent store, and how can i perform delete,edit operation on persistent stored data. 
Do not know what to, very much confused. Which approach will be best and what will the mechanism.
kindly suggest.