Table space segments (segments) Partitions (extent) blocks (blocks)

OracleTablespace (TableSpace), Segment (Segment), Disk Area (Extent), Block (Block).OracleThe allocation unit used to save database objects

SegmentIt is a database object that consumes storage space, such as tables, indexes, and rollback segments. When creating a table,Table segmentWhen a partition table is created, a segment is created for each partition. When an index is created, a partition is created.Index segment, Each object that consumes storage space is stored in a single segment.Rollback segment, temporary segment, clustering segment, and index segment.A segment can have disks from many inaccessible data files.

The segment itself consists of one or more disk zones, The disk area is allocated continuously in the file. Each segment must start at least one disk area, and some objects may need at least2Disks (such as rollback segments ). Each disk is not necessarily adjacent.

A disk is composed of blocks., OneThe block is inOracleThe smallest unit for space allocation in, YesOracleRead/write disk object,OracleNormally3Common sizes, 2 K, 4 K, 8 K.

A segment is composed of one or more disk areas, and a disk area is composed of some continuously allocated blocks.

A tablespace is a container that stores segments. Each segment exactly belongs to a tablespace. A tablespace can have multiple segments. All the disk partitions of a given segment are in the tablespace related to the segment. 

OracleThe hierarchical structure stored in is as follows:
1The database consists of one or more tablespaces.
2A tablespace is composed of one or more data files. A tablespace contains segments.
3A segment consists of one or more disk partitions. The segments exist in the tablespace, but many data files can exist in the tablespace.
4A disk is a continuous block group on a disk. A disk is in a tablespace and is always in a single file in the tablespace.
5Blocks are the smallest allocation units in the database, and blocks are the smallest units used by the database.I/OUnit.