Oracle storage management concepts Storage concepts in Oracle
	Data blocks: Data blocks are the smallest level of storage management. They map to operating system blocks. Extents: Extents are composed of contiguous blocks on a disk. Segments: A segment is typically associated with a single table or index. A segment can contain one or more extents. Tablespace: The tablespace is at the top of the storage hierarchy. A tablespace is directly connected with one or more datafiles, which are managed by the underlying operating system.