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What is a Data Warehouse? A data warehouse is a relational database that is designed for query and analysis rather than for transaction processing. It usually contains historical data derived from transaction data, but it can include data from other sources. It separates analysis workload from transaction workload and enables an organization to consolidate data from several sources.
In addition to a relational database, a data warehouse environment includes an extraction, transportation, transformation, and loading (ETL) solution, an online analytical processing (OLAP) engine, client analysis tools, and other applications that manage the process of gathering data and delivering it to business users.
A common way of introducing data warehousing is to refer to the characteristics of a data warehouse as set forth by William Inmon: n Subject Oriented n Integrated n Nonvolatile n Time Variant
Data Warehouse Architecture (Basic) Figure 1–2 shows a simple architecture for a data warehouse. End users directly access data derived from several source systems through the data warehouse. Figure 1–2 Architecture of a Data Warehouse In Figure 1–2, the metadata and raw data of a traditional OLTP system is present, as is an additional type of data, summary data. Summaries are very valuable in data warehouses because they pre-compute long operations in advance. For example, a typical data warehouse query is to retrieve something like August sales. Summaries in Oracle are called materialized views. Data Sources Warehouse Summary Data Raw Data Metadata