问题描述
Oracle数据库中表的高水位标记(HWM)是已使用的块与从未使用的块之间的界线.截断表会将HWM重置为零.
High Water Mark (HWM) for a table in an Oracle Database is the line between blocks that have been used and ones that have never been. Truncating a table resets the HWM to zero.
现在，如果我有一个分区表，我想知道以下情况是否正确:
Now, if I have a partitioned table, I'd like to know if the following is true:
- 每个分区都维护自己的HWM吗?
- 如果不是，
alter table ... drop partition ...是否会影响表的HWM?
- Does each partition maintain its own HWM?
- If not, does
alter table ... drop partition ...affect table's HWM?
这个想法是我想用insert /*+ append */(直接路径插入)填充分区的表，但是它只写HWM以外的数据，所以如果我重新创建分区，空间会被重用吗?我找不到有关此特定方面的信息.
The idea is I'd like to populate partition's tables with insert /*+ append */ (direct path insert), but it only writes data beyond the HWM, so will the space be reused if I recreate the partition? I failed to find information on this specific aspect.
推荐答案
每个分区都是一个单独的段，因此每个分区都有自己的HWM.我认为截断整个表将重置所有分区的HWM.您也可以截断单个分区，这肯定会重置该分区的HWM.
Each partition is a separate segment, so each would have its own HWM. I presume that truncating the whole table would reset the HWM for all partitions. You can truncate individual partitions as well, which certainly would reset the HWM for the partition.
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