working of delta in BW

Hello,

can somebody explain me how delta load works in BW.

starting from R/3 system, when a document is considered to be delats and the complete follow till BW. then how it behaves for an ODS and how it behaves for a CUBE.

In an ODS how it behaves for key figures which are overwrite and key figures which are addition.

also what is the role of reversal indicator and recordmode.

regards

Meps