Oracle logical Storage Structure

Oracle logical storage structures include tablespaces, various segments, intervals, data blocks, and other basic structures.
1) The tablespace is the logical division of the database. Each database has at least one tablespace, and the USER tablespace is used by general users. The RBS tablespace is used for rollback. One tablespace can only belong to one database. Each tablespace consists of one or more data files on the same disk. Tablespace is actually a way to organize data files.
2) segments are physical copies of logical database objects. segments store data, for example, index segments store index-related data.
3) A group of consecutive data blocks allocated by the database for segments is called an interval (extent)
4) data blocks are the hard disk storage units of Oracle databases. When using databases, Oracle uses data blocks to store and retrieve data on hard disks.

The following is a detailed description:

1. Database tablespace

The tablespace is the logical structure of data in the Oracle logical storage structure. The first database must have at least one system tablespace ). Tablespaces only help organize databases.
1) System tablespace is a required part and stores such table space names. Tablespaces contain data folders and other information required to manage the database.
2) temp tablespace: Oracle is used to store all its temporary tables.
3) tools tablespace: used to save the database objects required by the database tool software
4) User tablespace: used to store user information. It is the place where the database administrator permits the user to store database objects.
5) database index tablespace: The index is a dedicated database object that helps Oracle quickly find the data stored in the table.
6) rollback table space (rbs): The tablespace used to save the rollback segments. It is called the rbs tablespace for rollback.

2. segments, intervals, and data blocks

1) segments are composed of several intervals, which are continuous data blocks. Segments, intervals, and data blocks are the basic units that constitute other data objects. Oracle pre-allocates data files for database tablespaces as physical storage areas, and pre-allocates data block segments for database objects (such as tables and indexes) as their physical storage areas. Oracle databases can contain data segments, index segments, LOB segments, rollback segments, and temporary segments. Tables store data in Oracle logical storage structure data segments, and indexes store data in index segments, large objects store their corresponding LOB values in the LOB segment.

2) an interval is an adjacent data block allocated continuously in a tablespace. Because the segment is a physical entity, it must be allocated to a tablespace in the database and placed on a data file in the tablespace; once the existing range in the segment cannot accommodate new data, the segment will obtain another range.

3) data blocks
Datablock is the smallest and most basic storage unit in the database. It is the smallest storage unit that the database can allocate to objects and the smallest unit that Oracle can read or write from the disk. In Oracle, each data and index segment has one or more idle data blocks. It is the directory of idle data blocks and inserts a new row into the table, oracle places a new row in the data block in the table's idle list. If the row length is larger than the data block size, oracle connects to this row in two or more data blocks. When a new database object (such as a table) is created, Oracle assigns one or more intervals to the segments of these objects, the interval is a set of continuous data blocks in the data files that store the tablespace of these object segments.

Imagine a cabinet filled with stuff. The database is the Cabinet. The drawer in the Cabinet is the tablespace, the folder in the drawer is the data file, the paper in the folder is the table, and it is written on the paper.
Information is data, while tablespace is actually a way to organize files.

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