extraction in bw/bi

Hai guru's,

When data extracted from r/3 towards bi, for the following date 20,21,22. the scenario is on 20 and 22 it updated in data target on time. but on 21st data is not updated.

1.so if this is the case, what we need to do to update the data on 21st. where that data will be stored.

2.Is there any problem with process chain if we run the process chain for about scenario.

3.Is there any difference between generic and lo extraction will if the about scenario is used.

4.Is there any other possible errors will happen on above scenario.

please provide me the solution.

thanks in advance.

muthuselvan.r