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Segment Space Management in Locally Managed Tablespaces (51)

原创 IT综合 作者:tsinglee 时间:2007-09-30 14:43:57 0 删除 编辑

When you create a locally managed tablespace using the CREATE TABLESPACE
statement, the SEGMENT SPACE MANAGEMENT clause lets you specify how free and
used space within a segment is to be managed. Your choices are:
1 AUTO
This keyword tells Oracle that you want to use bitmaps to manage the free space
within segments. A bitmap, in this case, is a map that describes the status of each
data block within a segment with respect to the amount of space in the block
available for inserting rows. As more or less space becomes available in a data
block, its new state is reflected in the bitmap. Bitmaps enable Oracle to manage
free space more automatically; thus, this form of space management is called
automatic segment-space management.
Locally managed tablespaces using automatic segment-space management can be
created as smallfile (traditional) or bigfile tablespaces. AUTO is the default.
2 MANUAL
This keyword tells Oracle that you want to use free lists for managing free space
within segments. Free lists are lists of data blocks that have space available for
inserting rows.

lmt段空间管理
在创建表空间时 , 可通过SEGMENT SPACE MANAGEMENT字句来指定段空间的管理 , 有如下两种方式
1 auto : 使用位图(显示段内每个块为插入记录的保留空间的状态) , assm
2 manual : 使用free lists管理

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