ETL is the process used to create a data mart and data warehouse. In this process, the data is pulled from various data sources, then transformed into the required format by applying the business logic, and then stored back in the destination database, which could be the data warehouse.
The main element of this process is the staging area, because the pulled data gets stored in the staging area first and then the required transformation happens on that data. Once the transformation is finished, the output is stored in the destination database. Thus, the staging area plays an important role in ETL, and for the same reason, the staging area needs to be of good capacity for processing and storage.
Following diagram shows the ETL process:
