Page 56 - Demo

%u062c%u0645%u064a%u0639 %u0627%u0644%u062d%u0642%u0648%u0642 %u0645%u062d%u0641%u0648%u0638%u0629 %u0640 %u0627%u0625%u0644%u0639%u062a%u062f%u0627%u0621 %u0639%u0649%u0644 %u062d%u0642 %u0627%u0645%u0644%u0624%u0644%u0641 %u0628%u0627%u0644%u0646%u0633%u062e %u0623%u0648 %u0627%u0644%u0637%u0628%u0627%u0639%u0629 %u064a%u0639%u0631%u0636 %u0641%u0627%u0639%u0644%u0647 %u0644%u0644%u0645%u0633%u0627%u0626%u0644%u0629 %u0627%u0644%u0642%u0627%u0646%u0648%u0646%u064a%u062956Chapter FourData warehousing and Online Analytical ProcessingA data warehouse is a decision support database that is maintained separately from the organization%u2019s operational database, support information processing by providing a solid platform of consolidated, historical data for analysis. I. Data warehouse concepts Data warehouse is defined in many different ways. One of which is that a data warehouse is a subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management%u2019s decisionmaking process. Data warehouses (DWs) are focused on decision support rather than on transaction support. Data warehousing: is the process of constructing and using data warehouses. Subject-Oriented:- A data warehouse is organized around major subjects such as customer, supplier, product, and sales. Rather than concentrating on the day-today operations and transaction processing of an organization, a data warehouse focuses on the modeling and analysis of data for decision makers. Hence, data warehouses typically provide a simple and concise view of particular subject issues by excluding data that are not useful in the decision support process. Integrated:- A data warehouse is usually constructed by integrating multiple heterogeneous sources, such as relational databases, flat files, and online transaction records. Data cleaning and data integration techniques are applied to ensure consistency in naming conventions, encoding structures, attribute measures, and so on.Time-variant:- Data are stored to provide information from an historic perspective (e.g., the past 5%u201310 years). Every key structure in the data warehouse contains, either implicitly or explicitly, a time element But the key of operational data may or may not contain %u201ctime element%u2019%u2019 Nonvolatile:- A data warehouse is always a physically separate store of data transformed from the application data found in the operational environment. Due to this separation, a data warehouse does not require transaction processing, recovery, and concurrency control mechanisms.