案例环境：
案例描述：
通过块介质恢复（Block Media Recover:BMR)执行块级别的恢复操作来修复Oracle数据库上的逻辑或物理上损坏的数据块。
1、模拟数据块被破坏
10:26:48 SYS@ prod>conn scott/tiger
Connected.
10:26:51 SCOTT@ prod>select * from tab;
TNAME TABTYPE CLUSTERID
------------------------------ ------- ----------
BONUS TABLE
DEPT TABLE
EMP TABLE
EMP1 TABLE
SALGRADE TABLE
Elapsed: 00:00:00.10
10:26:55 SCOTT@ prod>
10:27:37 SYS@ prod>desc dba_segments
Name Null Type
----------------------------------------------------------------- -------- -------------
OWNER VARCHAR2(30)
SEGMENT_NAME VARCHAR2(81)
PARTITION_NAME VARCHAR2(30)
SEGMENT_TYPE VARCHAR2(18)
SEGMENT_SUBTYPE VARCHAR2(10)
TABLESPACE_NAME VARCHAR2(30)
HEADER_FILE NUMBER
HEADER_BLOCK NUMBER
BYTES NUMBER
BLOCKS NUMBER
EXTENTS NUMBER
INITIAL_EXTENT NUMBER
NEXT_EXTENT NUMBER
MIN_EXTENTS NUMBER
MAX_EXTENTS NUMBER
MAX_SIZE NUMBER
RETENTION VARCHAR2(7)
MINRETENTION NUMBER
PCT_INCREASE NUMBER
FREELISTS NUMBER
FREELIST_GROUPS NUMBER
RELATIVE_FNO NUMBER
BUFFER_POOL VARCHAR2(7)
FLASH_CACHE VARCHAR2(7)
CELL_FLASH_CACHE VARCHAR2(7)
10:27:41 SYS@ prod>col segment_name for a20
10:27:59 SYS@ prod>select owner,segment_name,SEGMENT_TYPE,HEADER_BLOCK from dba_segments
10:29:06 2 where owner='SCOTT' and segment_name='EMP1';
OWNER SEGMENT_NAME SEGMENT_TYPE HEADER_BLOCK
------------------------------ -------------------- ------------------ ------------
SCOTT EMP1 TABLE 170
通过以上查询，可以知道EMP1 table的segment header block为170；利用Uedit32，打开数据文件（users01.dbf)进行编辑破坏！
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
以下是计算block 170和block 171在Uedit32编辑中的offset：
10:29:24 SYS@ prod>select to_char(170*8*1024, 'xxxxxxxxxxxxxxxxxxxxx') from dual;
TO_CHAR(170*8*1024,'XX
----------------------
154000
10:30:27 SYS@ prod>select to_char(171*8*1024, 'xxxxxxxxxxxxxxxxxxxxx') from dual;
TO_CHAR(171*8*1024,'XX
----------------------
156000
以下是Uedit32编辑users01.dbf图片：
通过转储数据块验证：
10:30:37 SYS@ prod>alter system dump datafile 4 block 170;
System altered.
[oracle@rh6 ~]$ ls -lt /u01/app/oracle/diag/rdbms/prod/prod/trace/|more
total 14300
-rw-r----- 1 oracle oinstall 4492 Jul 15 1