What are Start routines, Transfer routines and Update routines?

—

Start Routines:

The start routine is run for each DataPackage after the data has been written to the PSA and before the transfer rules have been executed.
It allows complex computations for a key figure or a characteristic.
It has no return value. Its purpose is to execute preliminary calculations and to store them in global DataStructures.
This structure or table can be accessed in the other routines. The entire DataPackage in the transfer structure format is used as a parameter for the routine.

Transfer / Update Routines:

They are defined at the InfoObject level.
It is like the Start Routine.
It is independent of the DataSource.
We can use this to define Global Data and Global Checks.