利用BBED恢复UPDATE修改前的值

2021-10-21 08:38:35

实验过程如下：
1、创建表guo_test1

gyj@PROD> create table guoyJoe_t1(id int,name varchar2(10));
 
Table created.
 
gyj@PROD> insert into guoyJoe_t1 values(1,'guoyJoe');
 
1 row created.
 
gyj@PROD> insert into guoyJoe_t1 values(1,'tom');
 
1 row created.
 
gyj@PROD> COMMIT;
 
Commit complete.

2、查出这行记录的DBA


gyj@PROD> select name,dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,dbms_rowid.rowid_row_number(rowid)    row# from guoyJoe_t1;
 
NAME            FILE#     BLOCK#       ROW#
---------- ---------- ---------- ----------
guoyJoe             5      20877          0
tom                 5      20877          1
————————————————

3、刷数据缓存


gyj@PROD> alter system flush buffer_cache;
 
System altered.

4、利用BBED找到这行记录（修改前的值：guoyJoe）

BBED> BBED> set file 5    block 20877
        FILE#           5
        BLOCK#          20877

--观察行头
BBED> p kdbr
sb2 kdbr[0] @118 8074
sb2 kdbr[1] @120 8064

BBED> p *kdbr[0]

rowdata[10]

ub1 rowdata[10] @8174 0x2c

--观察事务
BBBED> x /rnc

rowdata[10] @8174

flag@8174: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8175: 0x01
cols@8176: 2

col 0[2] @8177: 1
col 1[7] @8180: guoyJoe

---观察空间
BBED> p kdbhavsp
sb2 kdbhavsp @110 8042

BBED> p kdbhtosp
sb2 kdbhtosp @112 8042

5、发生UPDATE语句，把原来的值guoyJoe修改成oracledba

gyj@PROD> update guoyJoe_t1 set name='oracledba' where name='guoyJoe';
 
1 row updated.
 
gyj@PROD> commit;
 
Commit complete

6、刷数据缓存

gyj@PROD> alter system flush buffer_cache;
 
System altered.

7、利用BBED找到这行被修改后的记录（修改后的值上：oracledba）


BBED> set file 5    block 20877
        FILE#           5
        BLOCK#          20877

--观察行头
BBED> p kdbr
sb2 kdbr[0] @118 8048
sb2 kdbr[1] @120 8064

BBED> p *kdbr[0]

rowdata[0]

ub1 rowdata[0] @8148 0x2c

--观察事务
BBED> x /rnc

rowdata[0] @8148

flag@8148: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8149: 0x01
cols@8150: 2

col 0[2] @8151: 1
col 1[9] @8154: oracledba

---观察空间
BBED> p kdbhavsp
sb2 kdbhavsp @110 8040

BBED> p kdbhtosp
sb2 kdbhtosp @112 8040

8、对比修改前与修改后的数据

BBED> d /v offset 8174 count 16
 File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)
 Block: 20877   Offsets: 8174 to 8189  Dba:0x0140518d
-------------------------------------------------------
 2c000202 c1020767 756f794a 6f650106 l ,...á..guoyJoe..
 
 
BBED> d /v offset 8148 count 16
 File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)
 Block: 20877   Offsets: 8148 to 8163  Dba:0x0140518d
-------------------------------------------------------
 2c010202 c102096f 7261636c 65646261 l ,...á..oracledba


9、开始恢复
（1）修改row directory指针位置（@118）
--修改前

BBED> p kdbr
sb2 kdbr[0]

                              @118      8074
--修改后
                                 @118      8048

BBED> p kdbr
sb2 kdbr[0]
g
yj@PROD> select to_char('8074','xxxxxxxxxxxxxx') from dual;

TO_CHAR('8074',

       1f8a

gyj@PROD> select to_char('8048','xxxxxxxxxxxxxx') from dual;

TO_CHAR('8048',

       1f70

BBED> d /v offset 118 count 16
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 118 to 133 Dba:0x0140518d

701f801f 00000000 00000000 00000000 l p...............

BBED> modify /x 8a offset 118
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) Y
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 118 to 133 Dba:0x0140518d

8a1f801f 00000000 00000000 00000000

<32 bytes per line>

BBED> sum apply
Check value for File 5, Block 20877:
current = 0x8a00, required = 0x8a00

BBED> verify
DBVERIFY - Verification starting
FILE = /u01/app/oracle/oradata/PROD/tp01.dbf
BLOCK = 20877

Block Checking: DBA = 20992397, Block Type = KTB-managed data block
data header at 0x7f76ff66e264
kdbchk: xaction header lock count mismatch ----事务锁报错

    trans=1 ilk=1 nlo=0

Block 20877 failed with check code 6108

DBVERIFY - Verification complete

Total Blocks Examined : 1
Total Blocks Processed (Data) : 1
Total Blocks Failing (Data) : 1
Total Blocks Processed (Index): 0
Total Blocks Failing (Index): 0
Total Blocks Empty : 0
Total Blocks Marked Corrupt : 0
Total Blocks Influx : 0
Message 531 not found; product=RDBMS; facility=BBED

2）接下来修改事务锁
---把更新前值的事务锁标记从00改为01

BBBED> x /rnc

rowdata[10] @8174

flag@8174: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8175: 0x01
cols@8176: 2

BBED> d /v offset 8175 count 16
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 8175 to 8190 Dba:0x0140518d

000202c1 02076775 6f794a6f 6501066f l ...á..guoyJoe..o

BBED> modify /x 01 offset 8175
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20861 Offsets: 8175 to 8190 Dba:0x0140517d

010202c1 02076775 6f794a6f 650106ed


--把更新后值的事务锁标识01改为00

BBED> x /rnc

rowdata[0] @8148

flag@8148: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8149: 0x01
cols@8150: 2

BBED> d /v offset 8149 count 16
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 8149 to 8164 Dba:0x0140518d

010202c1 02096f72 61636c65 6462612c l ...á..oracledba,

BBED> modify /x 00 offset 8149
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20861 Offsets: 8159 to 8174 Dba:0x0140517d

000202c1 02096f72 61636c65 6462612c

BBED> sum apply
Check value for File 5, Block 20877:
current = 0x8a00, required = 0x8a00
BBED> verify
DBVERIFY - Verification starting
FILE = /u01/app/oracle/oradata/PROD/tp01.dbf
BLOCK = 20877

Block Checking: DBA = 20992397, Block Type = KTB-managed data block
data header at 0x7cb464
kdbchk: the amount of space used is not equal to block size

    used=46 fsc=0 avsp=8040 dtl=8088 

---提示数据块的空间使用不正确（dtl-used=kdbhavsp=kdbhtosp）
       8088-46=8042 与 avsp=8040相关2,也就是说我要恢复到8042
     
 (3)修改空间，把空间修改为6a1f,以dtl-used=kdbhavsp为主

gyj@PROD> select to_char('8042','xxxxxxxxxxxxxx') from dual;

  TO_CHAR('8042',
   ---------------
       1f6a

BBED> modify /x 6a1f offset 110
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 110 to 125 Dba:0x0140518d

6a1f681f 00000200 8a1f801f 00000000

<32 bytes per line>

BBED> modify /x 6a1f offset 112
File: /u01/app/oracle/oradata/PROD/tp01.dbf (5)

Block: 20877 Offsets: 112 to 127 Dba:0x0140518d

6a1f0000 02008a1f 801f0000 00000000

<32 bytes per line>

BBED> sum apply
Check value for File 5, Block 20877:
current = 0x8a00, required = 0x8a00

BBED> verify
DBVERIFY - Verification starting
FILE = /u01/app/oracle/oradata/PROD/tp01.dbf
BLOCK = 20877

DBVERIFY - Verification complete

Total Blocks Examined : 1
Total Blocks Processed (Data) : 1
Total Blocks Failing (Data) : 0
Total Blocks Processed (Index): 0
Total Blocks Failing (Index): 0
Total Blocks Empty : 0
Total Blocks Marked Corrupt : 0
Total Blocks Influx : 0
Message 531 not found; product=RDBMS; facility=BBED

10、恢复成功（oracledba--->guoyJoe）

gyj@PROD> alter system flush buffer_cache;

System altered.

gyj@PROD> select name,dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,dbms_rowid.rowid_row_number(rowid) row# from guoyJoe_t1 where id=1;

NAME FILE# BLOCK# ROW#

guoyJoe 5 20877 0
tom 5 20877 1

实际上用BBED恢复UPDATE前的值不难，主要是要了解内部原理和块格式
总结如下：
 （1）修改行头
 （2）修改事务
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