... Oracle® Database Concepts 10g Release 1 (10.1)Part No. B10743-01December 2003xHow Views Are Used 5-18Mechanics ... SegmentsIntroduction to Data Blocks, Extents, and SegmentsOracle allocates logical database space for all data in a database. The units of database space allocation are data blocks, extents, and segments. Figure ... for guidelines onreclaiming segment space■Oracle Database SQL Reference for SQL syntax and semanticsOverview of Extents2-14 Oracle Database Concepts ■Periodically, Oracle deallocates one or...