hi,
I am developing stock control system. Recently, my client complain that my report generated very slowly. According to my investigation, it is because amount of data. This client has 25,000 products. Also, it could has 500 sales records and average 30 lineitems per sale within ONE DAY.
Therefore, I am worry about the performance of the query.
I was told that we should purge our data periodly.
Could you please give me some ideas?
Where does the purged data should be stored?
Could it able to be restored?
Once purged, how could I refer to previous data when necessary? Do you generate summary record for each table or...?

Pls advise

Thank you