we do not do urgent, and above all You did not tell the requirement
MDT set/reset is not related to map compilation
is a flag which is set by the hardware ( real or emulated ) when data is entered into a field
But any one can explain how to use it in program and what are the advantages and disadvantages of it??
the question is badly posed...
the issue is : what is the business need and what are the technical means to satisfy them
look like here we have a solution looking for a requirement
describe the requirement first, and afterward if the description is clear the solution will show up by itself