Designing a Data Warehouse. Issues in DW design. Data Warehouse. A read-only database for decision analysis Subject Oriented Integrated Time variant Nonvolatile consisting of time stamped operational and external data. . Highly tuned Real time Data Detailed records Current values
Issues in DW design
A read-only database for decision analysis
consisting of time stamped operational and external data.
An old idea with a new interest because of:
Cheap Computing Power
Special Purpose Hardware
New Data Structures
Contains operational data from all areas of the organization.
Extracted and managerial support data designed for departmental or EUC applications
Data required for a specific application
The storage component holds the data so that the many different data mining, executive information and decision support systems can make use of it effectively.
(decision support, artificial intelligence and expert systems)
Budgeting for systems analysis and development, however, follows a very different pattern.
Relational and Multidimensional Models
In most companies doing ROLAP, the DBAs have created countless indexes and summary tables in order to avoid I/O-intensive table scans against large fact tables. As the indexes and summary tables proliferate in order to optimize performance for the known queries and aggregations that the users perform, the build times and disk space needed to create them has grown enormously, often requiring more time than is allotted and more space than the original data!
Identify the data structure, attributes and constraints for the client’s data warehousing environment.
As always in life, there are some disadvantages to 3NF: