Forecasting and automatic reorder point planning

dear gurus... please help me with the following

1. We want to use forecasting now, how do we update past consumption data for all the fert items automatically from system.

2. how to run forecasting in mass for all the materials which are using automatic reorder point planning, how to do this as a background job so that the reorder points will get calculated and populated regularly.

3. how will the consumption figures get update regularly in future.

Regards

Abhishek