Data Warehousing

Data Warehousing

1. What is?

   • A data warehouse (DW) is a pool of data produced to support decision making; it is also a repository of current and historical data of potential interest to managers throughout the organization.

2. Characteristics

   • Subject oriented
     • Data are organized by detailed subject, such as sales, products, or customers, containing only information relevant for decision support.
   • Integrated
     • Data warehouses must place data from different sources into a consistent format.
   • Time variant (time series).
     • A warehouse maintains historical data.
   • Nouvolatile
     • After data are entered into a data warehouse, users cannot change or update the data.

3. Data Marts

   • A data mart is a subset of a data warehouse, typically consisting of a single subject area
   • Dependent Data Mart
     • Is a subset that is created directly from the data warehouse.
     • It has the advantages of using a consistent data model and providing quality data.
     • Support the concept of a single enterprise-wide data model
   • Independent data mart
     • Is a small warehouse designed for a strategic business unit or a department, but its source is not an EDW.

4. Operational Data Stores (ODS)

   • provides a fairly recent form of customer information file
   • Is often used as an interim staging area for a data warehouse.
   • Open marts (Imhoff, 2001) are created when operational data need to be analyzed multidimensionally. The data for an oper mart come from an ODS.

5. Enterprise Data Warehouses (EDWs)

   • An enterpdse data warehouse (EDW) is a large-scale data warehouse that is used across the enterprise for decision support.
   • The large-scale nature provides integration of data from many sources into a stanclarcl format for effective BI and decision support applications.

6. Metadata

   • Metadata describe the structure of and some meaning about data, thereby contributing to their effective or ineffective use.
   • Effectiveness, extensibility, reusability, interoperability, efficiency and performance, evolution, entitlement, flexibility, segregation, user interface