由 macro 发布于: 2001-03-04 17:05

The oracle database architecture includes logical and physical structures that make up the database.

1.The physical structure includes the control files,online redo log files ,and data files that make up the database.
2.The logical structure includes tablespaces,segments,extents,and data blocks.

The oracle server enables fine-grained control of disk space use through tablespace and logical storage structure ,include segments,extents,and data blocks.


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Macro Zeng

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我正在学习 Oracle ,坚持每天写读书笔记

由 macro 发布于: 2001-03-05 12:42

Tablespaces
The data in oracle database are stroed in tablespaces.

1.An oracle database can be logically grouped into smaller logical areas of space known as tablespace.

2.A tablespace can belong to only one database at a time.

3.Each tablespace consists of one or more operating system files,which are called datafile.

4. A tablespace can consist of one or more segments.

5.Tablespace can be brought online while the database is running.

6.Except for the SYSTEM tablespace or a tablespace with an artive rollback segment,tablespace can be taken offline,leaving the database running .

7.Tablespace can be switched between read-write and read-only status.
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我正在学习 Oracle ,坚持每天写读书笔记

由 macro 发布于: 2001-03-05 12:51

Data Files

1.A data file can belong to only one tablespace.

2.An oracle server creates a data file for a tablespace by allocating the specified amount of disk space plus a small amount of overhead.

3.The database administrator can change the size of a data file after its creation or can specify that a data file should dynamically grow as objects in the tablespace grow.
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我正在学习 Oracle ,坚持每天写读书笔记

由 macro 发布于: 2001-03-05 12:58

Segments

A segment is the space allocated for a specific logical storage structure within a tablespace.For example, all of the storage allocated to a table is segment.

1.A tablespace may consist of one or more segments.

2.A segment cannot span tablespace;howerver, a segment can span multiple data

3.Each segment is made up of one or more extents.
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由 macro 发布于: 2001-03-05 18:37

Extents
Space is allocated to a segment by extents.

1.One or more extents make up a segment.
-- When a segment is created,it consists of at least one exent.
-- As the segment grows,extents are added to the segment.
-- The DBA can manually add extents to a segment.

2.An extent is a set of contiguous oracle blocks.

3.An extent may not span a data file,but must exist in one data file.
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Macro Zeng

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我正在学习 Oracle ,坚持每天写读书笔记

由 macro 发布于: 2001-03-05 19:16

Data blocks

The oracle server manager the storage space in the data files in units called oracle blocks or data blocks.

1.At the finest level of granularity,the data in an oracle database is stored in data blocks.

2.Oracle data blocks are the smallest units of storage that the oracle server can allocate ,read or write.

3.One data block corresponds to one or more operating system blocks allocated from an existing data file.

4.Data block size is specified for each oracle database by the initialization parameter DB_BLOCK_SIZE when the database is created.

5.The data block size should be a multiple of the operating system block size to avoid unneccessary I/O.

6.The maximum data block size is dependent on the operating system.

__________________

谢谢你抽时间看我的发言，

Macro Zeng

==================================

我正在学习 Oracle ,坚持每天写读书笔记