Huge Data(250 GB) in a table

Hi,

we have 250 GB data in a table(partitioned day wise), which is only recent 3 months data, where not frequently queried by the application but if any request comes then only people fetch data from the table.so, instead of keeping such a big table in a DB, we would like to free up space in the DB,

So 1) need to be backed up by using RMAN or datapump, whenever we required then restore in the DB

     2) would like to keep the data in a various flat file (1 week of data each), then if requited queried from the flat file