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诚心求教，在线文档看了，看几遍还是不太理解，那位高手说说吧，
A segment and all its extents are stored in one tablespace. Within a tablespace, a segment can include extents from more than one file; that is, the segment can span datafiles. However, each extent can contain data from only one datafile.
Although you can allocate additional extents, the blocks themselves are allocated separately. If you allocate an extent to a specific instance, the blocks are immediately allocated to the free list. However, if the extent is not allocated to a specific instance, then the blocks themselves are allocated only when the high water mark moves. The high water mark is the boundary between used and unused space in a segment.
第二段特不明白呀 |
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楼主: blue_prince
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发表于 2009-1-16 09:17
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