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用Delete与Truncate清除表数据对高水位的影响

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Release: 2016-06-07 16:44:30
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众所周知,Oracle段都有一个在段内容纳数据块的上限,我们把这个上限称为High Water Mark(HWM)。这个HWM是一个标记,用来说明

从block_id字段的值可以发现,当在表中插入数据后,分配给表的block从128开始一直到1152,并且,开始的1-16个extent会以8个块(8*8=64K)为分配单位,而到了第17个extent之后,,则以128个块(8*128=1M)为分配单位,目前ZLM1表共分配了24个extent

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