本帖最后由 ninglin12 于 2013-1-10 13:51 编辑
An extent is a logical unit of database storage space allocation made up of a number of contiguous data blocks. One or more extents in turn make up a segment. When the existing space in a segment is completely used, Oracle allocates a new extent for the segment.
我也有这方面的疑惑,不过对于oracle把数据扩展的当成是一个弱化的概念(就是随意连续数据块的总称)