Overview

A Derby table or index (sometimes called a conglomerate) can contain unused space after large amounts of data have been deleted or updated. This happens because, by default, Derby does not return unused space to the operating system. Once a page has been allocated to a table or index, Derby does not automatically return the page to the operating system until the table or index is dropped, even if the space is no longer needed. However, Derby does provide a way to reclaim unused space in tables and associated indexes