SAP BW Communication Structure and Transfer Structure

When I first started dabbling with SAP BW, one of the questions that boggles my mind is "What's the difference between a Communication Structure (short: Comm Structure) and Transfer Structure?".

Well, transfer structure is like the data template of the source system. What it means is that, this transfer structure is exactly like the fields of the originating data. So, if you have a flat files with the fields: Cost Center, Business Area, Sales Amount, the transfer would be exactly like that. Also, in the transfer structure, you can have some conversion routine to convert for example, the date format of the originating data. Things like that.

But what about the communication structure? Why do we need it? Well, the answer to that my friend, is that, from the transfer structure, using a certain "transfer rules", we map the fields in the transfer structure to the communication structure. This communication structure is data-source independent, and this is what the "infocube" or the data targets would see. Not the transfer structure. Why is this good? Say, when extracting from legacy system, you still don't have in mind which fields you want to transfer and all. So, what you did is you transfer everything, which means that your transfer structure would be quite humongous. But, for now, you knew, you only need a few fields for reporting purposes.

So, in the communication structure, you will only select the "infoobjects" that you need, not all the fields in the transfer structure. In a way it acts as a filter for the transfer structure.

That, ladies and gentleman, is why you have a transfer structure and a communication structure.

11 comments:

Thu Feb 09, 11:44:00 PM 2006 Rafael said...

Congratulations on the way you explain SAP, never before have I understood as well, how could I get in touch with you, just a few words since I have started a career in SAP FI/CO is not easy and would like some general career advice.
Thank you.

Mon Feb 13, 10:42:00 AM 2006 ngising said...

you can email me at my email, in blogger profile.

Tue Mar 07, 08:26:00 PM 2006 Anonymous said...

very usefull, thanks a lot !

Thu Sep 14, 11:57:00 AM 2006 clueless said...

Very useful. And very detail. Thanks a lot.

Wed Dec 26, 03:01:00 AM 2007 Rajarathnam said...

wow thats a great way of explaining things dude!! :)

Tue Feb 19, 11:11:00 PM 2008 Anonymous said...

One word to describe the explination...Excellent!!!!!!!!!!!!!

Mon May 05, 01:55:00 PM 2008 Desigan said...

Thanks for this! Why cant they say it in the books like you did? Good stuff!

Tue Jun 24, 07:45:00 PM 2008 vinayak said...

WOW...WAT AN EXPLANATION!!!

Thu Aug 28, 09:16:00 PM 2008 silsa said...

but cant u do that filter in ur transfer str itself?do u mean that always transfer str will carry the entire data str from the source system?

Wed Nov 12, 08:48:00 PM 2008 ngising said...

you can choose how your transfer structure will look like for file datasource. But not for R/3 transfer structure.

But BI7, already eliminate these step. You only have transformation rule now which maps direct from datasource to the data target (if you want to, you can still map from infosource to data target).

Fri May 01, 05:24:00 AM 2009 Anonymous said...

There is one thing more to consider, and this is the generality and specificity (this is more about comparing transfer rules and update rules, however). Realize that you can create more update rules that are based on the same infosource (and even more, via these different update rules you can load to more cubes). Then, if you want to create some very general transformations for the loaded data, you can place it into transfer rule and the cube-specific transformations can be placed to update rules... The more near to the target in the load process, the more specific transformations...