Distributed Application with Delphi

Hi,

I plan to develop an application using Delphi. I will write my
application as distributed app. I will use MIDAS components, but there
are a few question in my mind and i cannot solve them.. Here are :

1. I dont know how i can control database transaction.
2. Which one is much faster ? A client-Server app. or distributed app
?
3. When i use TClientDataSet, i couldnt update a record to database.
Delphi says "use TClientDataset.ApplayUpdated(nmaxerr). I use it but
no effect and no record post database. I didnt see my changes on my
database..

Sincenerly
Adnan DURSUN
TURKEY..