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分类： Oracle
2006-12-19 17:24:56
1219-1. Read-Only Tablespaces
Because read-only tablespaces cannot be modified, and as long as they have not
been made read-write at any point, they do not need repeated backup. Also, if you
need to recover your database, you do not need to recover any read-only
tablespaces, because they could not have been modified.
（因为只读表空间不能修改，所以当它还没被设置成read-write的任一时刻他们都不需要备份。也就是说如果你需要恢复数据库，那么你不需要恢复只读表空间。）
-2. Transport of Tablespaces Between Databases（表空间传输）
A transportable tablespace lets you move a subset of an Oracle database from one
Oracle database to another on the same platform. You can clone a tablespace and
plug it into another database, copying the tablespace between databases, or you can
unplug a tablespace from one Oracle database and plug it into another Oracle
database, moving the tablespace between databases on the same platform.
（表空间传输能够让你在相同的平台下把ORACLE的表空间从一个数据库移动到另一个。你能够clone一个表空间并且把它挂载到另外的数据库，在数据库间复制表空间，也能从一个库去掉一个表空间挂载到另外的库，移动表空间的前提是必须处于相同的平台）
Moving data by transporting tablespaces can be orders of magnitude faster than
either export/import or unload/load of the same data, because transporting a
tablespace involves only copying datafiles and integrating the tablespace metadata.
When you transport tablespaces you can also move index data, so you do not have
to rebuild the indexes after importing or loading the table data.
（通过移动表空间来移动数据比exp/imp或者unload/load数据快一个数量级，因为移动一个表空间仅仅要解决的问题是复制数据文件和统一表空间的元数据。当传输表空间是相应的索引数居也可以移动，因此不用像Imp/load完数据后还要重建索引）
Note: You can transport tablespaces only between Oracle databases that use the same character set and that run on compatible platforms from the same hardware vendor.
（移动表空间时，两个数据库的字符集设置及他们运行的平台环境（包括软硬件环境）必须一致）
-3How to Move or Copy a Tablespace to Another Database
To move or copy a set of tablespaces, you must make the tablespaces read-only,
copy the datafiles of these tablespaces, and use export/import to move the database
information (metadata) stored in the data dictionary. Both the datafiles and the
metadata export file must be copied to the target database. The transport of these
files can be done using any facility for copying flat files, such as the operating
system copying facility, ftp, or publishing on CDs.
（移动或复制表空间前，必须使表空间处于只读状态，复制表空间的数据文件，使用exp/imp工具移动存储在数据字典里的数据库信息（元数据）。这些文件和信息必须复制到目标数据库。）
-4.Oracle allocates space for the data associated with a schema object in one or more datafiles of a tablespace.Therefore, a schema object can span one or more datafiles. Unless table striping is used (where data is spread across more than one disk), the database administrator and end users cannot control which datafile stores a schema object.
（Oracle给在一个表空间的一个或多个数据文件的schema object的所有数据分配空间，schema object能够跨越数据文件。Unless table striping is used (where data is spread across more than one disk)如何理解？数据库管理员和最终用户不能控制那个数据文件来存储那个schema object）
-5.Control Files Overview
.A control file is updated continuously by Oracle during database use, so it must be available for writing whenever the database is open.
（一个控制文件是不断的更新的当一个ORACLE数据库使用时，因此它必须在数据库打开的任何时候都处于可写状态）
-6. Control File Contents
Among other things, a control file contains information such as:
1）Datafile offline ranges
2）Backup set and backup piece information
3）The current log sequence number
