Firstly, if you came accidentally in this article it is paramount to clarify some expressions before starting to talk about the real subject that brought you here.
To begin with, DW is short for Data Warehouse which mean basically the physical place where all information from different sources is located. It will be used by BI (business intelligence) tools to analyse data and to deliver for the stakeholders insights and dashboard.
The DW is designed using multidimensional modelling, where data is organized in a way that makes it possible to find all necessary information easily. It is the DW aim, to allow the customers to access this information quickly and easily. Thus, the question is, how is all this data from different sources loaded, organized and inserted in a dimensional model?
In this moment, the ETL which is one of the most important steps of the process appears. It is responsible for Extracting from different sources, Transforming and organizing all information before Loading the data on DW. Well, if you have already read something about BI it is possible that you know that this process moves terabytes of data in average each transaction which happen once a day at least.
Hence, we can infer that every time that this process is executed, the concurrency increase because of high level processing and transactions. As a result, the production database becomes slow. Finally, after all these explanations we are going to talk about staging area.
A staging area is an intermediate storage area, it has a different database created specifically for this with its own rules to permit all kind of processes, aggregates, sums and counts for example. In other words, this is the database where the dirty work is done and to avoid some trouble with the production database, it is advised to use staging area in the ETL process.
Recapping, ETL is an important part of DW which takes data from different sources and loads it in a staging area, then it is processed and only after that the information is sent to DW.
In the end, it was possible to reach a reasonable conclusion to this interesting question, why I need a staging area in my DW.
Diogenes Santos.