利用BBED修改checksum值的过程

我在"利用dd修改checksum值的过程"一文中详细描述了如何用dd修改一个指定block的checksum值的过程，现在我用BBED把这个改坏了的checksum值再改回来，如下的是详细的修改过程：

上述文章里我用dd改完后，从alert log里确实可以看到checksum值不对了：

Corrupt block relative dba: 0x2140000b (file 133, block 11)

Bad check value found during buffer read

Data in bad block -

type: 6 format: 2 rdba: 0x2140000b

last change scn: 0x0008.a9d0a5ea seq: 0x1 flg: 0x06

consistency value in tail: 0xa5ea0601

check value in block header: 0xb72a, computed block checksum: 0x7000

spare1: 0x0, spare2: 0x0, spare3: 0x0

***

Reread of rdba: 0x2140000b (file 133, block 11) found same corrupted data

SQL_astca>select id from dras.t1;

----------

7 rows selected.

SQL_astca>BEGIN

2 DBMS_REPAIR.SKIP_CORRUPT_BLOCKS (

3 SCHEMA_NAME => 'DRAS',

4 OBJECT_NAME => 'T1',

5 OBJECT_TYPE => dbms_repair.table_object,

6 FLAGS => dbms_repair.NOSKIP_FLAG);

7 END;

8 /

PL/SQL procedure successfully completed.

SQL_astca>select id from dras.t1;

ERROR:

ORA-01578: ORACLE data block corrupted (file # 133, block # 11)

ORA-01110: data file 133: '/dras20/astca/test01.dbf'

no rows selected

SQL_astca>DECLARE num_fix INT;

2 BEGIN

3 num_fix := 0;

4 DBMS_REPAIR.FIX_CORRUPT_BLOCKS (

5 SCHEMA_NAME => 'DRAS',

6 OBJECT_NAME=> 'T1',

7 OBJECT_TYPE => dbms_repair.table_object,

8 REPAIR_TABLE_NAME => 'REPAIR_TABLE',

9 FIX_COUNT=> num_fix);

10 DBMS_OUTPUT.PUT_LINE('num fix: ' || to_char(num_fix));

11 END;

12 /

num fix: 0

PL/SQL procedure successfully completed.

SQL_astca>select id from dras.t1;

ERROR:

ORA-01578: ORACLE data block corrupted (file # 133, block # 11)

ORA-01110: data file 133: '/dras20/astca/test01.dbf'

no rows selected

这里可以看到用DBMS_REPAIR.FIX_CORRUPT_BLOCKS是不能修正一个block的checksum值错误的。

SQL_astca>shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL_astca>exit

Disconnected from Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit Production

With the Partitioning, OLAP and Oracle Data Mining options

JServer Release 9.2.0.6.0 - Production

好，现在我们来用BBED修改这个block的checksum值：

$ pwd

/cadrasu01/app/oracle/product/9.2.0/rdbms/lib

$ make -f ins_rdbms.mk $ORACLE_HOME/bin/bbed

make: 1254-002 Cannot find a rule to create target /cadrasu01/app/oracle/product/9.2.0/bin/bbed from dependencies.

Stop.

$ make -f ins_rdbms.mk BBED=$ORACLE_HOME/bin/bbed $ORACLE_HOME/bin/bbed

Linking BBED utility (bbed)

rm -f /cadrasu01/app/oracle/product/9.2.0/bin/bbed

ld -b64 -o /cadrasu01/app/oracle/product/9.2.0/bin/bbed -L/cadrasu01/app/oracle/product/9.2.0/rdbms/lib/ -L/cadrasu01/app/oracle/product/9.2.0/lib/ /cadrasu01/app/oracle/product/9.2.0/lib/s0main.o /cadrasu01/app/oracle/product/9.2.0/rdbms/lib/ssbbded.o /cadrasu01/app/oracle/product/9.2.0/rdbms/lib/sbbdpt.o `cat /cadrasu01/app/oracle/product/9.2.0/lib/ldflags` -lnsslb9 -lncrypt9 -lnsgr9 -lnzjs9 -ln9 -lnl9 /cadrasu01/app/oracle/product/9.2.0/rdbms/lib/defopt.o -ldbtools9 `cat /cadrasu01/app/oracle/product/9.2.0/lib/ldflags` -lnsslb9 -lncrypt9 -lnsgr9 -lnzjs9 -ln9 -lnl9 -lnro9 `cat /cadrasu01/app/oracle/product/9.2.0/lib/ldflags` -lnsslb9 -lncrypt9 -lnsgr9 -lnzjs9 -ln9 -lnl9 -lclient9 -lvsn9 -lwtc9 -lcommon9 -lgeneric9 -lwtc9 -lmm -lnls9 -lcore9 -lnls9 -lcore9 -lnls9 -lxml9 -lcore9 -lunls9 -lnls9 `cat /cadrasu01/app/oracle/product/9.2.0/lib/ldflags` -lnsslb9 -lncrypt9 -lnsgr9 -lnzjs9 -ln9 -lnl9 -lnro9 `cat /cadrasu01/app/oracle/product/9.2.0/lib/ldflags` -lnsslb9 -lncrypt9 -lnsgr9 -lnzjs9 -ln9 -lnl9 -lclient9 -lvsn9 -lwtc9 -lcommon9 -lgeneric9 -lpls9 -ltrace9 -lnls9 -lcore9 -lnls9 -lcore9 -lnls9 -lxml9 -lcore9 -lunls9 -lnls9 -lclient9 -lvsn9 -lwtc9 -lcommon9 -lgeneric9 -lnls9 -lcore9 -lnls9 -lcore9 -lnls9 -lxml9 -lcore9 -lunls9 -lnls9 -lld -lm `cat /cadrasu01/app/oracle/product/9.2.0/lib/sysliblist` -lm `if [ "\`/usr/bin/uname -v\`" = "4" ]; \

then echo "-bI:/cadrasu01/app/oracle/product/9.2.0/lib/pw-syscall.exp"; fi;` -lxsd9 /cadrasu01/app/oracle/product/9.2.0/lib/nautab.o /cadrasu01/app/oracle/product/9.2.0/lib/naeet.o /cadrasu01/app/oracle/product/9.2.0/lib/naect.o /cadrasu01/app/oracle/product/9.2.0/lib/naedhs.o

$ pwd

/cadrasu01/app/oracle/product/9.2.0/bin

$ cat filelist.txt

1 /dras11/oradata/astca/system01.dbf 524288000

125 /dras21/astca/system02.dbf 1048576000

133 /dras20/astca/test01.dbf 1048576

$ cat par.bbd

blocksize=8192

listfile=filelist.txt

mode=edit

bbed默认password是blockedit

$ bbed parfile=par.bbd

Password:

BBED: Release 2.0.0.0.0 - Limited Production on Mon Feb 23 14:54:56 2009

************* !!! For Oracle Internal Use only !!! ***************

BBED> set file 133

FILE# 133

BBED> set block 11

BLOCK# 11

BBED> set offset 16

OFFSET 16

BBED> show

FILE# 133

BLOCK# 11

OFFSET 16

DBA 0x2140000b (557842443 133,11)

FILENAME /dras20/astca/test01.dbf

BIFILE bifile.bbd

LISTFILE filelist.txt

BLOCKSIZE 8192

MODE Edit

EDIT Unrecoverable

IBASE Dec

OBASE Dec

WIDTH 80

COUNT 512

LOGFILE log.bbd

SPOOL No

BBED> modify /x 0xC7

File: /dras20/astca/test01.dbf (133)

Block: 11 Offsets: 16 to 527 Dba:0x2140000b

------------------------------------------------------------------------

c72a0000 01000000 00015020 a9d0a5e9 00080000 00020200 00000000 00050022

0001b6e8 12c0002a 46d40e00 20010000 a9d0a5ea 00000000 00000000 00000000

00000000 00000000 00000000 00010001 ffff0014 0821080d 080d0000 00010821

00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

<32 bytes per line>

BBED> sum apply

Check value for File 133, Block 11:

current = 0xc72a, required = 0xc72a

BBED> exit

$ sqlplus '/ as sysdba';

SQL*Plus: Release 9.2.0.6.0 - Production on Mon Feb 23 16:06:58 2009

Connected to an idle instance.

SQL_astca>startup

ORACLE instance started.

Total System Global Area 824150304 bytes

Fixed Size 743712 bytes

Variable Size 285212672 bytes

Database Buffers 536870912 bytes

Redo Buffers 1323008 bytes

Database mounted.

Database opened.

SQL_astca>select id from dras.t1;

----------

8 rows selected.

这里我们可以看到，checksum值已经被我们成功的改回来了！id为2的那条记录现在可以显示出来了！

2 Comments

hoterran | August 5, 2009 9:37 PM | Reply

sum apply 不就可以重新计算checksum 么？
为何还需要modify 这步呢？

cui hua replied to comment from hoterran | August 6, 2009 9:11 AM | Reply

你说的没错，sum apply的时候oracle会重新计算出正确的checksum值并写回去，我这里modify只是出于演示的目的。
关于checksum值的计算，你可以参考我写的另外一篇文章：
http://dbsnake.com/2009/06/compute-checksum.html

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Comments

cui hua: 你说的没错，sum apply的时候oracle会重新计算出正确的checksum值并写回去，我这里modify只是出于演示的目的。关于checksum值的计算，你可以参考我写的另外一篇文章： http://dbsnake.com/2009/06/compute-checksum.html read more
hoterran: sum apply 不就可以重新计算checksum 么？为何还需要modify 这步呢？ read more

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