Lesson 9

Clustering is a powerful technique for improving database performance.
Clustering is not for every type of table, but when it is used, it can significantly speed up queries. In this module, you learned:

1. The advantages of clustering
2. How to create and size a cluster
3. How to create a cluster key
4. The purpose of a hash cluster
5. How to create a hash cluster
6. How to drop a cluster

Tables and columns present a logical view of the data in a relational database. The flexibility of a relational database gives you many options for grouping the individual pieces of data, represented by the columns, into a set of tables. To use Oracle most effectively, you should understand and follow some firmly established principles of database design.
When E. F. Codd created the concept of a relational database in the 1960s, he also began work on the concept of normalized data design. The theory behind normalized data design is pretty straightforward:
A table should contain only the information that is directly related to the key value of the table. The process of assembling these logical units of information is called normalization of the database design.

There is more than one type of normalization. Each step in the normalization process ends with a specific result called a normalized form. There are five standard normalized forms, which are referred to as first normal form (1NF), second normal form (2NF), and so on. The normalization process that we describe briefly in this section results in third normal form (3NF), the most common type of normalization. Explaining the complete concepts that lie behind the different normal forms is beyond the scope of this module.
In the next module you will learn to create index-organized tables.

Click the Quiz link below to answer a few questions about hash clusters and dropping clusters.
Hash Cluster - Quiz