DWs are central repositories of integrated data from one or more disparate sources. The staging layer or staging database stores data warehousing concepts pdf free download data extracted from each of the disparate source data systems.
The integrated data are then moved to yet another database, often called the data warehouse database, where the data is arranged into hierarchical groups, often called dimensions, and into facts and aggregate facts. The access layer helps users retrieve data. Many references to data warehousing use this broader context. A data warehouse maintains a copy of information from the source transaction systems. Integrate data from multiple sources into a single database and data model. More congregation of data to single database so a single query engine can be used to present data in an ODS. Mitigate the problem of database isolation level lock contention in transaction processing systems caused by attempts to run large, long-running, analysis queries in transaction processing databases.
Integrate data from multiple source systems, enabling a central view across the enterprise. This benefit is always valuable, but particularly so when the organization has grown by merger. Present the organization’s information consistently. Provide a single common data model for all data of interest regardless of the data’s source. Restructure the data so that it makes sense to the business users. Optimized data warehouse architectures allow data scientists to organize and disambiguate repetitive data. Metadata, data quality, and governance processes must be in place to ensure that the warehouse or mart meets its purposes.
In regards to source systems listed above, R. Kelly Rainer states, “A common source for the data in data warehouses is the company’s operational databases, which can be relational databases”. Regarding data integration, Rainer states, “It is necessary to extract data from source systems, transform them, and load them into a data mart or warehouse”. Rainer discusses storing data in an organization’s data warehouse or data marts. Metadata are data about data. Today, the most successful companies are those that can respond quickly and flexibly to market changes and opportunities. A key to this response is the effective and efficient use of data and information by analysts and managers.