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Oracle block的类型

原创 Linux操作系统 作者:NinGoo 时间:2019-01-25 15:03:06 0 删除 编辑

我们知道,Oracle的最小IO单位是Block。在Oracle中,有多种block存在,比如file header block,segment header block,undo header block,data block,等等。那么,Oracle是根据什么来区别不同的block类型的呢?

每个Block的第一个字节就代表了该Block的类型。随着版本的进化,不断的有新的block类型产生,也有些旧的block类型消失。如果将每种block的内部存储结果弄清楚了,花点时间和耐心,要再写个dul也不是不可能的事情。

这两天抽空用c写了几行demo,基本上可以将普通的block dump出来,跟oracle自己提供的dump功能相似,只不过是可以脱机直接dump datafile的^_^

下表是从Ixora抄来的资料:


CodeBlock TypeVersions
1Undo header block (limited extents)all, but superseded by type 14 from 8.0
2Undo data blockall
3Save undo header block (limited extents)all, but superseded by type 15 from 8.0
4Save undo data blockall
5Data segment header block (limited extents, no freelist groups)all, but superseded by type 16 from 8.0
6Table/cluster/index segment data blockall
7Temporary segment data blockall
8Sort key blockall
9Sort run blockall
10Free list blockall, but superseded by type 22 from 8.0
11Data file header blockall
12Data segment header block (limited extents, with freelist groups)all, but superseded by type 17 from 8.0
13Compatibility segmentall
14Undo header block (unlimited extents)from 7.3
15Save undo header block (unlimited extents)from 7.3
16Data segment header block (unlimited extents, no freelist groups)from 7.3
17Data segment header block (unlimited extents, with freelist groups) from 7.3
18Extent map blockfrom 7.3
19Backup set piece headerfrom 8.0
20Backup set directory blockfrom 8.0
21Controlfile blockfrom 8.0
22Free list block with free block countfrom 8.0
23LOB segment header blockfrom 8.0
24LOB segment freelist blockfrom 8.0
25LOB segment space usage index blockfrom 8.0
26LOB segment space usage bitmap blockfrom 8.0
27LOB segment chunk data blockfrom 8.0
28don't know
29LMT space map header blockfrom 8.1
30LMT space map blockfrom 8.1
31don't know
32ASSM level 1 bitmap blockfrom 9.0
33ASSM level 2 bitmap blockfrom 9.0
34ASSM level 3 bitmap blockfrom 9.0
35ASSM segment header blockfrom 9.0
36ASSM extent map blockfrom 9.0
37don't know
38System managed undo header blockfrom 9.0

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