Data Conversion approach

 Dear All,

We are implementing a payroll solution for appx 300,000 Employees. We will need to convert data for all of them in 3 phases, with around 150,000 in one go.

We are considering two approaches and will like to know advantage and disadvantages of one over the other or anything better than this.

We have identified the components in Core HR, Base Benefits, Time & Labor and NA Payroll modules and will be loading data through AE/CIs. We will be developing a Data conversion framework which will help us load data in a component in multiple threads (AEs) simultaneously. 

Approach one:

Run Data Conversion process directly into the production during the go-live.