Abstract: A database system must be able to respond to requests for information from the user—i.e. process queries. Obtaining the desired information from a database system in a predictable and reliable fashion is Query Processing. To extract these results in a timely manner is possible with the technique of Query Optimization. For effective query processing the data must not be much fragmented. In this paper we focussed on the poor performance of query when the date fragmentation percentage is more and we have analysed how the fragmentation can be reduced using rebuild and re-organize techniques. In the last section, we have taken a sample data for query processing before rebuild and after that to have a comparative analysis.

Keywords: Indexing, Fragmentation, rebuild, re-organize.