Praim Sankar

• Sep 1st, 2005

 

Segments  
The level of logical database storage above an extent is called a segment. A segment is a set of extents which have been allocated for a specific type of data structure, and all are stored in the same tablespace. For example, each table's data is stored in its own data segment, while each index's data is stored in its own index segment. ORACLE allocates space for segments in extents. Therefore, when the existing extents of a segment are full, ORACLE allocates another extent for that segment. Because extents are allocated as needed, the extents of a segment may or may not be contiguous on disk, and may or may not span files. An extent cannot span files, though.