specific example on routine with unit

Hi gurus

I searched in forums for example on routine with unit in transformation and read master data routine.

since I am new to sap BI , I am not able to get a clear picture of the links.

could anyone please share to me specific examples on routine with unit(why is it done) & read master data routine(how it is implemented)?

any help would be greatly appreciated.

Points will be rewarded.

regards

krishna