ETL Process Overview
This chapter follows the flow of planning and implementing the ETL system. We implicitly discuss the 34 ETL subsystems presented in Chapter 19: ETL Subsystems and Techniques, broadly categorized as extracting data, cleaning and conforming, delivering for presentation, and managing the ETL environment.
Before beginning the ETL system design for a dimensional model, you should have completed the logical design, drafted your high-level architecture plan, and drafted the source-to-target mapping for all data elements.
The ETL system design process is critical. Gather all the relevant information, including the processing burden the extracts will be allowed to place on the operational source systems, and test some key alternatives. Does it make sense to host the transformation process on the source system, target system, or its own platform? What tools are available on each, and how effective are they?