DATA WAREHOUSING:

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  • A data warehouse is a relational database that acts as a repository for archive of information gathered from multiple sources, stored under a unified schema under a single site
  • It is being designed for query, data analysis and reporting rather than for transaction processing.
  • Data warehouses store current and historical data which are derived from transactional data and are used for creating trending reports for senior management reporting
  • 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.
  • The typical Extract-Transform-Load (ETL)-based data warehouse uses staging, data integration, and access layers to house its key functions
    • Staging: The staging layer or staging database stores raw data extracted from each of the disparate source data systems.
    • Data Integration: The integration layer integrates the disparate data sets by transforming the data from the staging layer often storing this transformed data in an operational data store (ODS) database. 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 combination of facts and dimensions is sometimes called a star schema.
    • Access Layer: The access layer helps users retrieve data.
  • It separates analysis workload from transaction workload and enables an organization to consolidate data from several sources.
  • Data warehousing incorporates data stores and conceptual, logical, and physical models to support business goals and end-user information needs.
  • The data stored in the warehouse is uploaded from the operational systems
  • The data may pass through an operational data store for additional operations before it is used in the DW for reporting.
  • A data mart is a small data warehouse focused on a specific area of interest. Data warehouses can be subdivided into data marts for improved performance and ease of use within that area.

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