请教undo segment中transaction table slots的数量？

显示全部楼层 · 2012-1-4 11:56:44

在一本书中看到，transaction table slots in an undo segment in 11g的数量是34。
有两个问题：
1.这个数量是怎么得来的？如何查看？
2.在10g中transaction table slots in an undo segment是多少？
多谢！

千问 · 2012-1-4 11:56:44

这两个问题都可以用一种方法解决，找到回滚段头的位置，alter system dump datafile ... block ....，然后查看DUMP结果就可以了。
如何用视图查看，我也不太清楚。

千问 · 2012-1-4 11:56:44

vage 发表于 2012-5-14 11:59
这两个问题都可以用一种方法解决，找到回滚段头的位置，alter system dump datafile ... block ....，然后查 ...
是不是一个undo segment在同一时间最多只能支持34个事务？

千问 · 2012-1-4 11:56:44

vage 发表于 2012-5-14 11:59
这两个问题都可以用一种方法解决，找到回滚段头的位置，alter system dump datafile ... block ....，然后查 ...
谢谢V哥
我做了一个update操作，然后dump undo段头(alter system dump undo header '_SYSSMU8$'

，
结果如下：
********************************************************************************
Undo Segment:_SYSSMU8$ (8)
********************************************************************************
Extent Control Header
-----------------------------------------------------------------
Extent Header:: spare1: 0spare2: 0#extents: 3#blocks: 143

last map0x00000000#maps: 0offset: 4080
Highwater::0x00800455ext#: 2blk#: 76 ext size: 128
#blocks in seg. hdr's freelists: 0
#blocks below: 0
mapblk0x00000000offset: 2

Unlocked
Map Header:: next0x00000000#extents: 3obj#: 0flag: 0x40000000
Extent Map
-----------------------------------------------------------------
0x0080007alength: 7
0x00800011length: 8
0x00800409length: 128
Retention Table
-----------------------------------------------------------
Extent Number:0Commit Time: 1336824669
Extent Number:1Commit Time: 1336827633
Extent Number:2Commit Time: 1336827633
TRN CTL:: seq: 0x0293 chd: 0x0008 ctl: 0x0016 inc: 0x00000000 nfb: 0x0001

mgc: 0x8201 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe)

uba: 0x00800455.0293.1c scn: 0x0000.006fe83b
Version: 0x01
FREE BLOCK POOL::
uba: 0x00000000.0293.1b ext: 0x2spc: 0x124c
uba: 0x00800452.0293.0e ext: 0x2spc: 0x4ca
uba: 0x00000000.0293.05 ext: 0x2spc: 0xa68
uba: 0x00000000.0286.01 ext: 0x2spc: 0x1f88
uba: 0x00000000.0000.00 ext: 0x0spc: 0x0
TRN TBL::

indexstate cflagswrap#uel scn
dba
parent-xidnub stmt_numcmt
------------------------------------------------------------------------------------------------
0x0090x000x0d560x00030x0000.006fe95a0x008004510x0000.000.000000000x00000001 0x000000001336850991
0x0190x000x0d550x00110x0000.006fe9d10x008004510x0000.000.000000000x00000001 0x000000001336851100
0x0290x000x0d560x00270x0000.006fe89e0x008004510x0000.000.000000000x00000001 0x000000001336850800
0x0390x000x0d530x00010x0000.006fe98a0x008004510x0000.000.000000000x00000001 0x000000001336851040
0x0490x000x0d580x00170x0000.006ff16a0x008004520x0000.000.000000000x00000001 0x000000001336852813
0x0590x000x0d590x001b0x0000.006ff5b20x008004550x0000.000.000000000x00000001 0x000000001336853273
0x0690x000x0d540x002b0x0000.006fee6a0x008004510x0000.000.000000000x00000001 0x000000001336852191
0x0790x000x0d5b0x001f0x0000.006feb690x008004510x0000.000.000000000x00000001 0x000000001336851461
0x0890x000x0d560x00020x0000.006fe8870x008004500x0000.000.000000000x00000001 0x000000001336850800
0x0990x000x0d550x00200x0000.006fed860x008004510x0000.000.000000000x00000001 0x000000001336852002
0x0a90x000x0d580x00000x0000.006fe9360x008004510x0000.000.000000000x00000001 0x000000001336850980
0x0b90x000x0d550x00070x0000.006feb2f0x008004510x0000.000.000000000x00000001 0x000000001336851401
0x0c 100x800x0d580x00020x0000.006ff6530x008004550x0000.000.000000000x00000001 0x000000000
0x0d90x000x0d590x00290x0000.006fecbc0x008004510x0000.000.000000000x00000001 0x000000001336851822
0x0e90x000x0d580x00060x0000.006fee540x008004510x0000.000.000000000x00000001 0x000000001336852191
0x0f90x000x0d590x002f0x0000.006ff3260x008004550x0000.000.000000000x00000001 0x000000001336852843
0x1090x000x0d580x002c0x0000.006fef740x008004510x0000.000.000000000x00000001 0x000000001336852423
0x1190x000x0d570x001c0x0000.006fea060x008004510x0000.000.000000000x00000001 0x000000001336851160
0x1290x000x0d580x00040x0000.006ff1690x008004550x0000.000.000000000x00000003 0x000000001336852813
0x1390x000x0d5b0x00240x0000.006fefe40x008004510x0000.000.000000000x00000001 0x000000001336852542
0x1490x000x0d540x002d0x0000.006ff0b70x008004520x0000.000.000000000x00000001 0x000000001336852723
0x1590x000x0d590x00190x0000.006fedf60x008004510x0000.000.000000000x00000001 0x000000001336852122
0x1690x000x0d560xffff0x0000.006ff5f40x008004550x0000.000.000000000x00000001 0x000000001336853293
0x1790x000x0d5b0x00250x0000.006ff28f0x008004550x0000.000.000000000x00000001 0x000000001336852816
0x1890x000x0d580x000b0x0000.006feb0b0x008004510x0000.000.000000000x00000001 0x000000001336851365
0x1990x000x0d530x000e0x0000.006fee2c0x008004510x0000.000.000000000x00000001 0x000000001336852182
0x1a90x000x0d560x00090x0000.006fed390x008004510x0000.000.000000000x00000001 0x000000001336851942
0x1b90x000x0d590x00160x0000.006ff5cf0x008004550x0000.000.000000000x00000001 0x000000001336853274
0x1c90x000x0d5a0x00180x0000.006fea410x008004510x0000.000.000000000x00000001 0x000000001336851220
0x1d90x000x0d570x00210x0000.006fec0e0x008004510x0000.000.000000000x00000001 0x000000001336851641
0x1e90x000x0d540x001d0x0000.006febd40x008004510x0000.000.000000000x00000001 0x000000001336851581
0x1f90x000x0d590x001e0x0000.006feb9f0x008004510x0000.000.000000000x00000001 0x000000001336851521
0x2090x000x0d580x00150x0000.006feda10x008004510x0000.000.000000000x00000001 0x000000001336852006
0x2190x000x0d570x00220x0000.006fec470x008004510x0000.000.000000000x00000001 0x000000001336851701
0x2290x000x0d560x000d0x0000.006fec7d0x008004510x0000.000.000000000x00000001 0x000000001336851761
0x2390x000x0d5b0x00260x0000.006ff3810x008004550x0000.000.000000000x00000001 0x000000001336852903
0x2490x000x0d580x00280x0000.006ff06f0x008004520x0000.000.000000000x00000001 0x000000001336852660
0x2590x000x0d570x002a0x0000.006ff2c40x008004550x0000.000.000000000x00000001 0x000000001336852843
0x2690x000x0d540x002e0x0000.006ff40e0x008004550x0000.000.000000000x00000001 0x000000001336853028
0x2790x000x0d570x000a0x0000.006fe8ff0x008004510x0000.000.000000000x00000001 0x000000001336850919
0x2890x000x0d580x00140x0000.006ff0830x008004520x0000.000.000000000x00000001 0x000000001336852663
0x2990x000x0d550x001a0x0000.006fecf60x008004510x0000.000.000000000x00000001 0x000000001336851882
0x2a90x000x0d540x000f0x0000.006ff3020x008004550x0000.000.000000000x00000001 0x000000001336852843
0x2b90x000x0d4f0x00100x0000.006fef5c0x008004510x0000.000.000000000x00000001 0x000000001336852422
0x2c90x000x0d560x00130x0000.006fefac0x008004510x0000.000.000000000x00000001 0x000000001336852482
0x2d90x000x0d570x00120x0000.006ff0fc0x008004520x0000.000.000000000x00000001 0x000000001336852783
0x2e90x000x0d560x00050x0000.006ff5750x008004550x0000.000.000000000x00000001 0x000000001336853213
0x2f90x000x0d550x00230x0000.006ff3420x008004550x0000.000.000000000x00000001 0x000000001336852843
没有找到，不知道是不是我功力还不够？

千问 · 2012-1-4 11:56:44

ahdong2007 发表于 2012-5-14 12:26
是不是一个undo segment在同一时间最多只能支持34个事务？
我是这么理解的。不知道是否正确

千问 · 2012-1-4 11:56:44

从 0x00到 0x2f 的，就是事务Slot了，是47个。也就是说，一个回滚段，最多支持47个事务。

千问 · 2012-1-4 11:56:44

ahdong2007 发表于 2012-5-14 12:26
是不是一个undo segment在同一时间最多只能支持34个事务？
根据LZ的DUMP结果，应该是47个事务

千问 · 2012-1-4 11:56:44

vage 发表于 2012-5-14 19:48
从 0x00到 0x2f 的，就是事务Slot了，是47个。也就是说，一个回滚段，最多支持47个事务。
那是否意味着，一个undo表空间，默认分为10个segment，最多只能同时支持470个事务？
那好像也太少了吧？

千问 · 2012-1-4 11:56:44

本帖最后由 vage 于 2012-5-14 19:58 编辑
回滚段会越来越多的啊。随着事务越来越多，回滚段也会越来越多的。
不会保持10个不变的，除非回滚段表空间已经快没空间了。

千问 · 2012-1-4 11:56:44

vage 发表于 2012-5-14 19:58
回滚段会越来越多的啊。随着事务越来越多，回滚段也会越来越多的。
不会保持10个不变的，除非回滚段表空间 ...