When you cluster data, you store frequently combined records from different tables as close together on the computer's hard drive as possible. The downside to clustering records from different tables is that records from the same table are no longer stored close to each other on the disk, which affects performance:

1. Clustering slows down operations that require the RDBMS to search an entire table.
2. Clustering may slow down data insertion because the RDBMS must search the disk for the last record in the table.
3. Clustering may increase the time needed to update data in the fields used to define the cluster because the RDBMS must determine again which records to include in the cluster.

The next lesson introduces partitioning.

Before you move on to the next lesson, click the Quiz link below to reinforce your understanding of clustering.
Clustering Disadvantages - Quiz