'78938c58' sqlid='7bd391hat42zk'
select /*+ rule */ name,file#,block#,status$,user#,undosqn,xactsqn,scnbas,scnwrp,DECODE(inst#,0,NULL,inst#),ts#,spare1 from undo$ where us#=:1
END OF STMT
PARSE #2:c=0,e=17,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=3,plh=906473769,tim=1414654507002839
BINDS #2:
Bind#0
oacdty=02 mxl=22(22) mxlc=00 mal=00 scl=00 pre=00
oacflg=08 fl2=0001 frm=00 csi=00 siz=24 off=0
kxsbbbfp=7fcf70adc448 bln=22 avl=02 flg=05
value=7 undo段的状态是从undo$基表中获取的，那么我们看看这里的基表对应的物理块号
SYS@orcl11g>select rowid,dbms_rowid.rowid_object(rowid) robject,
2 dbms_rowid.rowid_relative_fno(rowid) fno,
3 dbms_rowid.rowid_block_number(rowid) bno,
4 dbms_rowid.rowid_row_number(rowid) rno from undo$ where rownum=1;
ROWID ROBJECT FNO BNO RNO
------------------ ---------- ---------- ---------- ----------
AAAAAPAABAAAADhAAA 15 1 225 0
然后我们使用bbed查看该数据块：
BBED> map
File: /opt/oracle/oradata/orcl11g/system01.dbf (1)
Block: 225 Dba:0x004000e1
------------------------------------------------------------
KTB Data Block (Table/Cluster)
struct kcbh, 20 bytes @0
struct ktbbh, 48 bytes @20
struct kdbh, 14 bytes @68
struct kdbt[1], 4 bytes @82
sb2 kdbr[21] @86
ub1 freespace[3752] @128
ub1 rowdata[4308] @3880
ub4 tailchk @8188
这里可以看出与视图对应的21个回滚段：
BBED> p kdbr
sb2 kdbr[0] @86 8078
sb2 kdbr[1] @88 4071
sb2 kdbr[2] @90 5156
sb2 kdbr[3] @92 5088
sb2 kdbr[4] @94 4206
sb2 kdbr[5] @96 4952
sb2 kdbr[6] @98 4341
sb2 kdbr[7] @100 4816
sb2 kdbr[8] @102 4748
sb2 kdbr[9] @104 4680
sb2 kdbr[10] @106 4611
sb2 kdbr[11] @108 4008
sb2 kdbr[12] @110 5880
sb2 kdbr[13] @112 5817
sb2 kdbr[14] @114 5751
sb2 kdbr[15] @116 3943
sb2 kdbr[16] @118 5622
sb2 kdbr[17] @120 3878
sb2 kdbr[18] @122 5490
sb2 kdbr[19] @124 3812
sb2 kdbr[20] @126 5360
BBED> p *kdbr[10]
rowdata[799]
------------
ub1 rowdata[799] @4679 0x2c
BBED> x /1rnnnnnnnn
rowdata[799] @4679
------------
flag@4679: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@4680: 0x00
cols@4681: 17
col 0[2] @4682: 10
col 1[21] @4685: -0
col 2[2] @4707: 1
col 3[2] @4710: 3
col 4[3] @4713: 272
col 5[5] @4717: 5168854
col 6[1] @4723: 0
col 7[3] @4725: 866
col 8[3] @4729: 350
col 9[1] @4733: 0
col 10[2] @4735: 3
col 11[2] @4738: 2
col 12[0] @4741: *NULL*
col 13[0] @4742: *NULL*
col 14[0] @4743: *NULL*
col 15[0] @4744: *NULL*
col 16[2] @4745: 2
在这里我们将回滚段的状态修改为2，表示offline
BBED> modify /x 02 offset 4737
Warning: contents of previous BIFILE will be lost. Proceed (Y/N) y
File: /opt/oracle/oradata/orcl11g/system01.dbf (1)
Block: 225 Offsets: 4737 to 5248 Dba:0x004000e1
------------------------------------------------------------------------
0202c103 ffffffff 02c1032c 011102c1 0a145f53 5953534d 55395f31 34323433
34313937 352402c1 0202c104 03c20339 05c40614 12210180 03c20b5e 03c2045e
018002c1 0302c103 ffffffff 02c1032c 001102c1 09145f53 5953534d 55385f32
30313233 38323733 302402c1 0202c104 03c20329 05c40614 11380180 03c20b40
03c20334 018002c1 0302c103 ffffffff 02c1032c 001102c1 08145f53 5953534d
55375f33 32383636 31303036 302402c1 0202c104 03c20319 05c40614 11350180
03c20953 03c20418 018002c1 0302c103 ffffffff 02c1032c 001102c1 07145f53
5953534d 55365f32 34343333 38313439 382402c1 0202c104 03c20309 05c40220
295a0180 03c20944 03c20261 018002c1 0402c10