bbed 找回被删除数据

创建模拟表数据

SQL> create table t_xifenfei(id number,name varchar2(10));

Table created.

SQL> insert into t_xifenfei values(1,'xifenfei');

1 row created.

SQL> insert into t_xifenfei values(2,'XIFENFEI');

1 row created.

SQL> commit;

Commit complete.

dump数据块

SQL> alter system flush BUFFER_CACHE;

System altered.

SQL> select   rowid,id,name,
  2  dbms_rowid.rowid_relative_fno(rowid)rel_fno,
  3  dbms_rowid.rowid_block_number(rowid)blockno,
  4  dbms_rowid.rowid_row_number(rowid) rowno
  5  from chf.t_xifenfei;

ROWID                      ID NAME          REL_FNO    BLOCKNO      ROWNO
------------------ ---------- ---------- ---------- ---------- ----------
AAASdmAAEAAAACvAAA          1 xifenfei            4        175          0
AAASdmAAEAAAACvAAB          2 XIFENFEI            4        175          1

SQL> alter system dump datafile 4 block 175;

System altered.

dump文件内容

block_row_dump:
tab 0, row 0, @0x1f89
tl: 15 fb: --H-FL-- lb: 0x1  cc: 2
col  0: [ 2]  c1 02
col  1: [ 8]  78 69 66 65 6e 66 65 69
tab 0, row 1, @0x1f7a
tl: 15 fb: --H-FL-- lb: 0x1  cc: 2
col  0: [ 2]  c1 03
col  1: [ 8]  58 49 46 45 4e 46 45 49
end_of_block_dump
2012-05-01 05:09:29.287714 : kjbmbassert [0xaf.4]
End dump data blocks tsn: 4 file#: 4 minblk 175 maxblk 175

删除表数据

SQL> delete from t_xifenfei;

2 rows deleted.

SQL> commit;

Commit complete.

SQL> alter system flush BUFFER_CACHE;

System altered.

SQL> alter system dump datafile 4 block 175;

System altered.

dump文件内容

block_row_dump:
tab 0, row 0, @0x1f89
tl: 2 fb: --HDFL-- lb: 0x2 
tab 0, row 1, @0x1f7a
tl: 2 fb: --HDFL-- lb: 0x2 
end_of_block_dump
2012-05-01 05:13:35.214357 : kjbmbassert [0xaf.4]
End dump data blocks tsn: 4 file#: 4 minblk 175 maxblk 175

通过对比这两次的dump文件发现

1.数据内容被删除,并不是真正删除,而是给其增加了一个标识位(fd:---D----)
2.fb:--H-FL--(head of row piece+first data piece+last data piece )
  其有8个选项每个选项的值分别对应bitmask即32+8+4=44 or 0x2c
3.如果一个row被delete了,那么row flag就会更新,bitmask里的deleted被设置为16.
  此时row flag为：32+16+8+4 = 60 or 0x3c.
4.如果我们要找回来被删除的数据,只需要把3c改为2c即可

关闭数据库

SQL> select * from chf.t_xifenfei;

no rows selected

SQL> select name from v$datafile where file#=4;

NAME
------------------------------------------------
/tmp/user01.dbf

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

bbed修改数据

BBED> set filename '/tmp/user01.dbf'
        FILENAME        /tmp/user01.dbf

BBED> set block 175
        BLOCK#          175

BBED> set blocksize 8192
        BLOCKSIZE       8192

BBED> set mode edit
        MODE            Edit

BBED> map 
 File: /tmp/user01.dbf (0)
 Block: 175                                   Dba:0x00000000
------------------------------------------------------------
 KTB Data Block (Table/Cluster)

 struct kcbh, 20 bytes                      @0       

 struct ktbbh, 72 bytes                     @20      

 struct kdbh, 14 bytes                      @100     

 struct kdbt[1], 4 bytes                    @114     

 sb2 kdbr[2]                                @118     

 ub1 freespace[8036]                        @122     

 ub1 rowdata[30]                            @8158    

 ub4 tailchk                                @8188    

BBED> p *kdbr[0]
rowdata[15]
-----------
ub1 rowdata[15]                             @8173     0x3c

BBED> p *kdbr[1]
rowdata[0]
----------
ub1 rowdata[0]                              @8158     0x3c

BBED> m /x 2c offset 8158
 File: /tmp/user01.dbf (0)
 Block: 175              Offsets: 8158 to 8191           Dba:0x00000000
------------------------------------------------------------------------
 2c630202 c1030858 4946454e 46454932 630202c1 02087869 66656e66 65690106 
 b47e 

 <32 bytes per line>

BBED>  m /x 2c offset 8173
 File: /tmp/user01.dbf (0)
 Block: 175              Offsets: 8173 to 8191           Dba:0x00000000
------------------------------------------------------------------------
 2c630202 c1020878 6966656e 66656901 06b47e 

 <32 bytes per line>

BBED> sum apply
Check value for File 0, Block 175:
current = 0x4d13, required = 0x4d13

启动数据库验证

SQL> startup 
ORACLE instance started.

Total System Global Area  535662592 bytes
Fixed Size                  1346140 bytes
Variable Size             411043236 bytes
Database Buffers          117440512 bytes
Redo Buffers                5832704 bytes
Database mounted.
Database opened.
SQL> select * from chf.t_xifenfei;

        ID NAME
---------- ----------
         1 xifenfei
         2 XIFENFEI