Hi venkat ,
After compression data moves to F fact table to E face table.
if you want delete the data form cube after compression use selective deletion based on the some char (ex:calday, calmonth, calyear) it is possible.
based on which object your loading data from dso to info cube.
Request reverse posting is possible in BW 3.x and not possible in BI 7.0./3.
Thanks,
Phani.