Hi
For one, Batch Data Communication (BDC) is older. Business Application Programming Interface (BAPI) came later, about 10 years ago (you can see this already from the name, which contains marketese like "business" ).
More important though, they are different technologies. With BDC you build the "batch input transaction" yourself, with an ABAP program which creates the "batch input session" ("Batch-Input-Mappe" in german). You then take that session, like an object, and "run" it on a system (most of the time, this is done on a local system by the administrators, after it has been tested for correctness).
With BAPI, a system (local or remote) exposes its interface to you through some kind of Remote Function Call (RFC). Practically, it tells you: "What do you want to do? Insert that data into Materials Management? Here is the function and the the parameters you have to use for each record". You only work with the Interface - the exposed function. How this function works does not have to interest you. You don't have sessions to "run", you fire your function calls filled with data, one after another and you're done.
BAPI can be run remotely. With BDC, you probably have to call the administrators of the remote system and send them the session you created for them to run. With BDC you go through the whole transaction in one BDC session, with BAPI you may need more than one "BAPI calls" to do this.
With BAPI you don't fill obcure field names with values, you just fill the parameters. You can use a BAPI from inside your ABAP program to let a "business object" do some clearly defined work for you, then you can continue with your code doing other things. You don't do this with BDC. With BDC you write a dedicated program that creates the "session", which is then executed separately.
A BAPI is a method of a SAP Business Object. BAPI enables SAP and third party applications to interact and integrate
with each other at the Business Object / Process level.
Check this link to know more about BAPI.
http://www.sapgenie.com/abap/bapi/example.htm
http://sappoint.com/abap/
Batch Data Communication (BDC) is the oldest batch interfacing technique that SAP provided since the early versions of R/3. BDC is not a
typical integration tool, in the sense that, it can be only be used for uploading data into R/3 and so it is not bi-directional.
BDC works on the principle of simulating user input for transactional screen, via an ABAP program. Typically the input comes in the form
of a flat file. The ABAP program reads this file and formats the input data screen by screen into an internal table (BDCDATA). The
transaction is then started using this internal table as the input and executed in the background.
In ‘Call Transaction’, the transactions are triggered at the time of processing itself and so the ABAP program must do the error handling.
It can also be used for real-time interfaces and custom error handling & logging features. .
To know more about BDC,
check the link.
http://sappoint.com/abap/
Main differences are...
In case of bdc data transfer takes place from flat file into sap system ie the file existing in sap system to sap sytem
where is bapi's r remotly enabled function modules which are assigned to some business objects n used to transfer the data between different business partners who are using different systems other than sap.
not only that...
when you plan to upgrade your system version then bdc willnot support those upgradations where as bapi's will support.
Reward all helpfull answers
Regards
Pavan
Bluesky