SAP Data Services landscape and architecture

Hi there,

simple question:

A data migration has to be done from one SAP ERP source system to an SAP ERP  target system.

Source and target systems have DEV - QA - PRD environment.

Do we require also DEV / QA / PRD environment for SAP DS?

and transport projects&repositories bz ATL/files from one environment to another?

Or is 1 SAP DS box enough since the datastores allow multiple settings for different source&target systems and

we can switch between the different settings?

What is usual and what is best practice?

Thanks for explanation!

Andrzej