When you click the Delete button on the Currency Exchange Rate form, you will get a message warning you that you are about to delete the line item your cursor is on. You have the option at this point to cancel or go ahead and delete the selected record. If you confirm that you want to delete the selected record, VisionCore will delete it and there will be No way of retrieving that record again.
The Delete button can be disabled so that other users can't delete any of the Currency Exchange Rates. You can enable or disable the Permission checkbox for Delete Currency Exchange Rates in the Security form, Form Permission Tab (under System module).