Data Access Layer & Data Layer

[puresmile]

what is the difference between Data Access Layer & Data Layer??

[DNA7433]

Nothing

[puresmile]

Nothing

how..........?there is difference. can u plz explain ur point of view more

[DNA7433]

Oh you know what, I know what you mean now. The Data Layer is your database. The Data Access Layer is a layer of code in your program that encapsulates and handles all interaction with the database

[puresmile]

Oh you know what, I know what you mean now. The Data Layer is your database. The Data Access Layer is a layer of code in your program that encapsulates and handles all interaction with the database

yes that what i want to confirm, what abt ODBC etc i think it's separate middle layer

[DNA7433]

ODBC is a data access technology that your code inside the Data Access Layer can utilize to connect to your data source. Same as ADO.

Your DAL is specific to each project while technologies such as ADO work for any project without modification.

[puresmile]

ODBC is a data access technology that your code inside the Data Access Layer can utilize to connect to your data source. Same as ADO.

Your DAL is specific to each project while technologies such as ADO work for any project without modification.

ok, now coming to the purpose of my question, when say 3-tier architecture

1. Presentation Layer
2. Business Layer
3. Data Layer

but in coding perspective; we define 3-tier architecture

1. Presentation Layer
2. Business Logic Layer
3. Data Access Layer

one cay say; why are you saying two different layers at 3 place!!! since there is a difference in b/w two. how should we satify them??

[DNA7433]

3-tier architecture is when there is a machine running the database, another machine running the server side functionality (business layer) and each user runs the presentation layer on his computer. Splitting it up accross computers allows the application to scale more easily (when your number of users increases) because you can add more computers to say just the business layer to process the requests. In a web scenario you can have several machines for the database, several machines handling web requests using your business layer (which in turn use the database machines) and the presentation layer is the user's browser. The business and data access layers of the software usually run on the same machine.

3-layer architecture in software is exactly as you say. The presentation layer is where the code for the user interface goes, business logic layer is where your business objects go, and data access layer is where the code to transfer data between the database and your business objects go.

I hope that helps.