We are using data upload wizard in APEX 4.1. It is taking too long while going from Mapping to validation page. We tried with a file which has 34000 records and 5 columns. It takes more than an hour to load.
You're going to need to provide more information before people can help.
What's your table structure?
Does it have any indexes or constraints?
What sort of mapping are you doing?
Do these tables have indexes?