Hi Gaurav,
I doubt this because i have seen the 'N' occurring more than once in the logs as well.
Rather i checked and found that the system automatically chooses the best delete mode. This is N or D.
If you want to delete more than 10% of the records, the system creates a new table, copies the data records you want to keep to the new table, deletes the old table and then renames the new table. (This is where N will come) and If you want to delete less than 10% of the data records, the system deletes these individual records directly from the InfoCube fact table (This is the case where D will come).