In a classic data warehouse, this zone is usually a database and/or a schema in it that used to hold a copy of the data from the source systems. The staging area is necessary because most of the time, data sources are not stored on the same server as the data warehouse. Even if they are on the same server, we prefer a copy of them for the following reasons:
- Preserve data integrity. All data is copied over from a specific point in time. This ensures that we have consistency between tables.
- We might need specific indexes that we could not create in the source system. When we query the data, we're not necessarily making the same links (joins) in the source system. Therefore, we might have to create indexes to increase query performance. ...
