What Is a Data Warehouse?
1-2 Oracle Database 2 Day + Data Warehousing Guide
What This Guide Is Not
Oracle Database 2 Day + Data Warehousing Guide is not an exhaustive discussion of
implementing a data warehouse on Oracle. The objective for this guide is to describe
why and when tasks must be performed in a task-oriented way. Where appropriate, it
describes the concepts necessary for understanding and completing the current task.
For complete conceptual information about these features and detailed instructions for
using them, see the appropriate Oracle documentation as follows:
■ Oracle Database Data Warehousing Guide
■ Oracle Warehouse Builder Sources and Targets Guide
■ Oracle Database Administrator's Guide for a discussion of administrative tasks
■ Oracle Data Mining Concepts for a discussion of data mining
What Is a Data Warehouse?
A data warehouse is a relational or multidimensional database that is designed for
query and analysis. Data warehouses are not optimized for transaction processing,
which is the domain of OLTP systems. Data warehouses usually consolidate historical
and analytic data derived from multiple sources. Data warehouses separate analysis
workload from transaction workload and enable an organization to consolidate data
from several sources.
A data warehouse usually stores many months or years of data to support historical
analysis. The data in a data warehouse is typically loaded through an extraction,
transformation, and loading (ETL) process from one or more data sources such as
OLTP applications, mainframe applications, or external data providers.
Users of the data warehouse perform data analyses that are often time-related.
Examples include consolidation of last year's sales figures, inventory analysis, and
profit by product and by customer. More sophisticated analyses include trend analyses
and data mining, which use existing data to forecast trends or predict futures. The data
warehouse typically provides the foundation for a business intelligence environment.
This guide covers relational implementations, including star schemas.
The Key Characteristics of a Data Warehouse
The key characteristics of a data warehouse are as follows:
■ Some data is denormalized for simplification and to improve performance
■ Large amounts of historical data are used
■ Queries often retrieve large amounts of data
■ Both planned and ad hoc queries are common
■ The data load is controlled
In general, fast query performance with high data throughput is the key to a successful
data warehouse.
See Also: Oracle Database Data Warehousing Guide for more details
regarding multidimensional data warehouses
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