[20190213]学习bbed-恢复删除的数据.txt
–//以前也做过类似测试,当时在用bbed做verify时错误都不处理,当时的想法就是能读出就ok了.
–//而且当时也做成功,纯粹是依葫芦画瓢,按照别人的blog重复操作,一点不理解为什么这样做.
–//重复测试:
1.环境:
scott@book> @ ver1
port_string version banner
—————————— ————– ——————————————————————————–
x86_64/linux 2.4.xx 11.2.0.4.0 oracle database 11g enterprise edition release 11.2.0.4.0 – 64bit production
scott@book> create table dept1 as select * from dept ;
table created.
scott@book> select rowid,dept1.* from dept1;
rowid deptno dname loc
—————— ———- ————– ————-
aaawpyaaeaaaailaaa 10 accounting new york
aaawpyaaeaaaailaab 20 research dallas
aaawpyaaeaaaailaac 30 sales chicago
aaawpyaaeaaaailaad 40 operations boston
scott@book> @ rowid aaawpyaaeaaaailaaa
object file block row rowid_dba dba text
———- ———- ———- ———- ——————– ——————– —————————————-
91122 4 523 0 0x100020b 4,523 alter system dump datafile 4 block 523 ;
scott@book> delete from dept1 where deptno=10;
1 row deleted.
scott@book> commit ;
commit complete.
scott@book> alter system checkpoint ;
system altered.
2.使用bbed恢复测试:
bbed> set dba 4,523
dba 0x0100020b (16777739 4,523)
bbed> x /rncc *kdbr[1]
rowdata[44] @8140
———–
flag@8140: 0x2c (kdrhfl, kdrhff, kdrhfh)
lock@8141: 0x00
cols@8142: 3
col 0[2] @8143: 20
col 1[8] @8146: research
col 2[6] @8155: dallas
bbed> x /rncc *kdbr[0]
rowdata[66] @8162
———–
flag@8162: 0x3c (kdrhfl, kdrhff, kdrhfd, kdrhfh)
lock@8163: 0x02
cols@8164: 0
–//可以看出删除的flag=0x3c(正常没有发生行链接或者迁移的情况下).
bbed> assign offset 8162=0x2c;
warning: contents of previous bifile will be lost. proceed? (y/n) y
ub1 rowdata[0] @8162 0x2c
bbed> x /rncc *kdbr[0]
rowdata[66] @8162
———–
flag@8162: 0x2c (kdrhfl, kdrhff, kdrhfh)
lock@8163: 0x02
cols@8164: 3
col 0[2] @8165: 10
col 1[10] @8168: accounting
col 2[8] @8179: new york
–//ok,现在已经正常读出.
bbed> sum apply
check value for file 4, block 523:
current = 0x8dc2, required = 0x8dc2
bbed> verify
dbverify – verification starting
file = /mnt/ramdisk/book/users01.dbf
block = 523
block checking: dba = 16777739, block type = ktb-managed data block
data header at 0x7f9b8221527c
kdbchk: the amount of space used is not equal to block size
used=118 fsc=24 avsp=7946 dtl=8064
block 523 failed with check code 6110
–//以前verify出错,我基本不做修复,因为这些数值不是很好理解.
–//实际上计算公司是
–//dtl-used-fsc=avsp 或者 used+fsc+avsp=dtl.
–//8064-118-24 = 7922
–//前面显示(lock@8163: 0x02)事务使用itl槽是1(从0开始记数).
bbed> p ktbbh.ktbbhitl[1]
struct ktbbhitl[1], 24 bytes @68
struct ktbitxid, 8 bytes @68
ub2 kxidusn @68 0x000a
ub2 kxidslt @70 0x0007
ub4 kxidsqn @72 0x000058bf
struct ktbituba, 8 bytes @76
ub4 kubadba @76 0x00c001e4
ub2 kubaseq @80 0x11ad
ub1 kubarec @82 0x1d
ub2 ktbitflg @84 0x2001 (ktbfupb)
union _ktbitun, 2 bytes @86
sb2 _ktbitfsc @86 24
ub2 _ktbitwrp @86 0x0018
ub4 ktbitbas @88 0x1775b85d
–//_ktbitfsc,_ktbitwrp类似c语言的union,当设置提交标识时,表示scn_wrap.其它表示dml操作回收的空间(不包括flag,lock标识).
–//如果insert或者update需要空间比原来大,记录是0.
bbed> x /rncc *kdbr[0]
rowdata[66] @8162
———–
flag@8162: 0x2c (kdrhfl, kdrhff, kdrhfh)
lock@8163: 0x02
cols@8164: 3
col 0[2] @8165: 10
col 1[10] @8168: accounting
col 2[8] @8179: new york
–//1+1+2+1+10+1+8 = 24,正好等于回收空间.注意每个字段前有1个长度指示器(如果字符串长度大于250,需要3个字节)
bbed> assign ktbbh.ktbbhitl[1]._ktbitun._ktbitfsc=0;
sb2 _ktbitfsc @86 0
bbed> sum apply
check value for file 4, block 523:
current = 0x8dda, required = 0x8dda
bbed> verify
dbverify – verification starting
file = /mnt/ramdisk/book/users01.dbf
block = 523
block checking: dba = 16777739, block type = ktb-managed data block
data header at 0x1a98e7c
kdbchk: space available on commit is incorrect
tosp=7972 fsc=0 stb=0 avsp=7946
block 523 failed with check code 6111
–//计算公式是tosp=fsc+stb+avsp,stb 标识什么不理解.
bbed> p kdbh
struct kdbh, 14 bytes @124
ub1 kdbhflag @124 0x00 (none)
sb1 kdbhntab @125 1
sb2 kdbhnrow @126 4
sb2 kdbhfrre @128 -1
sb2 kdbhfsbo @130 26
sb2 kdbhfseo @132 7972
sb2 kdbhavsp @134 7946
sb2 kdbhtosp @136 7972
bbed> assign kdbhtosp=kdbhavsp;
sb2 kdbhtosp @136 7946
bbed> assign kdbh.kdbhtosp=kdbh.kdbhavsp;
sb2 kdbhtosp @136 7946
–//两者写法都支持.
bbed> sum apply
check value for file 4, block 523:
current = 0x8df4, required = 0x8df4
bbed> verify
dbverify – verification starting
file = /mnt/ramdisk/book/users01.dbf
block = 523
–//ok.
scott@book> alter system flush buffer_cache;
system altered.
scott@book> select rowid,dept1.* from dept1;
rowid deptno dname loc
—————— ———- ————– ————-
aaawpyaaeaaaailaaa 10 accounting new york
aaawpyaaeaaaailaab 20 research dallas
aaawpyaaeaaaailaac 30 sales chicago
aaawpyaaeaaaailaad 40 operations boston
–//随便说一下,不要再使用modify修改信息,这样非常容易出错(要考虑大小头问题).使用assign简单快捷,很少出错.
–//简直就像小时候玩变形金刚的游戏.