Oracle Logical Structure (1) Table Space Overview

1. Table Space (tablespace)

A table space is a basic logical structure in a database, a collection of data files. A table space can contain multiple data files, but a data file can belong to only one table space.

Query table space:

Sql>select * Form Dba_data_files;

Query table space for idle information:

Sql>select * from Dba_free_space;

Sql>alter tablespace * * * *? Offline

Limit table space Size:

Sql>alter User * * * * Quota ***m on * * *

The temporary tablespace is used by the order BY statement that is sorted for the user. You can specify the default temporary tablespace for the database when you create the database. You can specify a user's default temporary tablespace when creating a user. For example, the following sentence specifies the temp table space for the user.

Sql>create USER * * * * Identified by * * * Temporary tablespace temp;

2, paragraph (Segment)

The segment is the space that the object occupies in the database, although the segment and the database object are one by one corresponding, but the segment is from the database storage point of view. A segment can only belong to one table space, and of course a table space may have multiple segments.

Table spaces and data files are one-to-many relationships on physical storage, and table spaces and segments are one-to-many relationships on logical storage, and segments do not directly relate to data files. A segment can belong to more than one data file, and the paragraph can specify which data file to extend to.

Paragraph can be divided into the following four kinds of basic

Data segment (Segment)

Indexed Segment (Index Segment)

Rollback segment (Rollback Segment)

Temporary segment (Temporary Segment)

3. Interval (Extent)

There are many explanations for the translation of extent, some translations are extended, and some translations are in the area, which I usually translate into intervals. There can be multiple intervals in a segment, the interval is a large storage space reserved for data once, until that interval is filled, and the database continues to request a new reserved storage space, that is, the new interval, up to the maximum interval of the segment (Max Extent) or no available disk space to request. In the oracle8i version, theoretically a segment can be infinite, but multiple intervals have a performance impact on Oracle, and Oracle proposes to distribute the data

In as few intervals as possible, to reduce Oracle's management and head movement.

4. Oracle Data blocks (block)

Oracle's most basic storage unit, which is an integer multiple of the OS data block. Oracle operates on a block-by-unit basis, and an interval can contain multiple blocks (if the interval size is not an integer multiple of the block size, Oracle actually extends to the integer multiple of the block).

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