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<HEAD><TITLE>论坛精华 >> Oracle 专栏 >> A 8-1 Database Storage Hierarchy</title>
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>> A 8-1 Database Storage Hierarchy [<a href=http://www.jsp001.com/forum/showthread.php?goto=newpost&threadid=602>查看别人的评论</a>]<br>
<hr><p>由 macro 发布于: 2001-03-04 17:05</p><p> </p><p>The oracle database architecture includes logical and physical structures that make up the database.<br><br>1.The physical structure includes the control files,online redo log files ,and data files that make up the database.<br>2.The logical structure includes tablespaces,segments,extents,and data blocks.<br><br>The oracle server enables fine-grained control of disk space use through tablespace and logical storage structure ,include segments,extents,and data blocks.<br><br><br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p><hr><p>由 macro 发布于: 2001-03-05 12:42</p><p> </p><p>Tablespaces<br>The data in oracle database are stroed in tablespaces.<br><br>1.An oracle database can be logically grouped into smaller logical areas of space known as tablespace.<br><br>2.A tablespace can belong to only one database at a time.<br><br>3.Each tablespace consists of one or more operating system files,which are called datafile.<br><br>4. A tablespace can consist of one or more segments.<br><br>5.Tablespace can be brought online while the database is running.<br><br>6.Except for the SYSTEM tablespace or a tablespace with an artive rollback segment,tablespace can be taken offline,leaving the database running .<br><br>7.Tablespace can be switched between read-write and read-only status.<br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p><hr><p>由 macro 发布于: 2001-03-05 12:51</p><p> </p><p>Data Files<br><br>1.A data file can belong to only one tablespace.<br><br>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.<br><br>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.<br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p><hr><p>由 macro 发布于: 2001-03-05 12:58</p><p> </p><p>Segments<br><br>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.<br><br>1.A tablespace may consist of one or more segments.<br><br>2.A segment cannot span tablespace;howerver, a segment can span multiple data <br><br>3.Each segment is made up of one or more extents.<br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p><hr><p>由 macro 发布于: 2001-03-05 18:37</p><p> </p><p>Extents <br>Space is allocated to a segment by extents.<br><br>1.One or more extents make up a segment.<br> -- When a segment is created,it consists of at least one exent.<br> -- As the segment grows,extents are added to the segment.<br> -- The DBA can manually add extents to a segment.<br><br>2.An extent is a set of contiguous oracle blocks.<br><br>3.An extent may not span a data file,but must exist in one data file.<br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p><hr><p>由 macro 发布于: 2001-03-05 19:16</p><p> </p><p>Data blocks<br><br>The oracle server manager the storage space in the data files in units called oracle blocks or data blocks.<br><br>1.At the finest level of granularity,the data in an oracle database is stored in data blocks.<br><br>2.Oracle data blocks are the smallest units of storage that the oracle server can allocate ,read or write.<br><br>3.One data block corresponds to one or more operating system blocks allocated from an existing data file.<br><br>4.Data block size is specified for each oracle database by the initialization parameter DB_BLOCK_SIZE when the database is created.<br><br>5.The data block size should be a multiple of the operating system block size to avoid unneccessary I/O.<br><br>6.The maximum data block size is dependent on the operating system.<br><br>__________________<br><br>谢谢你抽时间看我的发言，<br><br>Macro Zeng<br><br>==================================<br><br>我正在学习 Oracle ,坚持每天写读书笔记</p></td>
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