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.

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

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

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

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