What is Clustering? What are its types.

CLUSTERING: If the page containing the requested record is already in the memory, retrieval from the disk is not necessary. In such a situation time taken for the whole operation will be less. Thus, if records which are frequently used together are placed physically together, more records will be in the same page. Hence the number of the pages to be retrieved is less and this reduces the number of disk accesses which intern gives a better performances. “The method of storing logically related records, physically together is called clustering.”

Types of Clustering::

• INTRA FILE CLUSTERING: - Clustered records belong to the same file.
• INTER FILE CLUSTERING: - Clustered records belong to different files. This type of clustering may be required to enhance the speed of queries retrieving related records from more than one table. Here interleaving records is used.