thanks both for your inputs,
We did some more analysis. Yes there was an transport. There was change in one of our table and along with that table the application was saved in the transport. even though there were no changes in other tables the data was wiped out of all the tables including the table which was changed.
When we are running the Factory methods to read the data; we get the data from process_pure method. But the method was last generated in august 2014. So i think the method not re-generating has saved us lot of effort 
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Just one thing we would like to know is that does transporting application mean that all the tables will regenerate with data refresh even though we haven't made any change?