Ok I understand now:

UI - communicates with business layer and users (Presentation)
Business layer - it's middle layer, it's between UI and Data layer (Business Logic)
Data Layer - it only communicates with Data Storage (DataBase)

My question is:

If I use CA (Up to now, I use CA with 3-Layered design and without ADO but with ODBC!) with ADODB and 3-Layered design (User Interface, Business Logic and Data Layer), in this case where is there (placed) ADODB commands like oConn.Open(),oConn.BeginTrans(),
oRS.ActiveConnection = oConn, oRS.UpdateBatch(), oConn.RollbackTrans(), oRS.CancelBatch(), oConn.CommitTrans()... (which layer?)?
In this case (with ADO commands) is unnecessary CA ?

See you my preliminary mail for details and simple code for CA.Init().

Best regards and thanks for help !
Vojislav