will perform update of large number of objects in one transaction and for each updated
object shadow is created, then it leads to significant increase of database file size.
If you update each object in the database inside one transaction, database size will be 
almost doubled! And if you perform each update in separate transaction, then size of database
will be almost unchanged (because space of allocated shadow objects will be reused in this case).
So the best approach is to perform commit after 100 or 10