This post explains how the BDC works under the hood.
It does however miss out on fully updating the underlying data – you need to update each BDC field explicitly.
It does however miss out on fully updating the underlying data – you need to update each BDC field explicitly.
The big flaw with the BDC is that the externally referenced data is cached in the list itself. The user needs to update the list (which can be time consuming) or the host app must do it for the user.
Developer Rants 