Strategies to import big data into Oracle
You didn't mention how the data comes in, but I would hazard a guess that it is through flat files. If this is the case, I worked at an order processing company that used Oracle for the back-end of the WMS we used. We regularly received 10 of millions of records a day. 
We used SQL loader scripts to load the data. The caveat to that is that the data needs to be in the proper format. See here:

http://knoworacle.blogspot.com/2012/05/oracle-sql-loader-with-example.html

And of course from the makers:

http://docs.oracle.com/cd/B10501_01/text.920/a96518/aload.htm