谢谢，我刚才看深入数据库体系结构时看到"Oracle 会全表扫描至HWM，对于low HWM以下的所有块会直接读取并加以处理。而对介于低HWM和low HWM之间的块，则必须更加小心"，我以为他直接读取low HWM下面的所有数据然后不知道删除了咋办。 然后在听完你说再看遍定义“The low high water (low HWM) s the point below which all blocks are known to be formatted because they either contain data or formerly contained data.”英语渣，现在才知道formerly代表的大概意思
然后在听完你说再看遍定义“The low high water (low HWM) s the point below which all blocks are known to be formatted because they either contain data or formerly contained data.”英语渣，现在才知道formerly代表的大概意思