Journal of Accounting and Management Information Systems (JAMIS)

The use of clustering technique in databases

Supp/2006 ,   p763..775


Keywords:   cluster, hash cluster, cluster key, cluster index, optimization, data access

In this paper we analyze the utility of clustering technique applied in Oracle databases. We analyze the concept .of clustering techniques, its different forms, and how they apply in IT, especially in databases. We bring into discussion technical issues associated with cluster (and hash cluster) definition, such as cluster key, cluster index, hash functions. As far as performance consideration and data storage are concerned, clusters offer two main advantages when used correctly: the output time is better for joins defined on clustered tables and the space needed for data storage is reduced because the cluster key values (which are defined using the common columns of the clustered tables) are stored only once, no matter how many rows correspond to the same value of the cluster key. Clusters have disadvantages as well, such as the potential of reducing the performance of update/insert/delete statements. We analyze the cases in which clusters should and should not be used in an attempt of finding the point at which the advantages of using a cluster overweight the disadvantages of it.