1.怎么计算出正确的checksum值？

bingwangzi2500 · 发表于 2019-7-14 14:51

SQL> create table hdb12.test1(id int,name varchar2(10));

Table created.

SQL> insert into hdb12.test1 values(1,'hdb');

1 row created.

SQL> commit;

Commit complete.

select dbms_rowid.rowid_relative_fno(rowid) file_id,
   dbms_rowid.rowid_block_number(rowid) block_id,
   dbms_rowid.rowid_row_number(rowid)
   from hdb12.test1;

FILE_ID BLOCK_ID DBMS_ROWID.ROWID_ROW_NUMBER(ROWID)
---------- ---------- ----------------------------------
12          26243          0

SQL> alter system flush buffer_cache;

System altered.

BBED> set file 12 block 26243
  FILE#          12
  BLOCK#          26243

BBED> map /v
File: /data/ORCL/datafile/hdb02.dbf (12)
Block: 26243                               Dba:0x03006683
------------------------------------------------------------
KTB Data Block (Table/Cluster)

struct kcbh, 20 bytes                   @0
ub1 type_kcbh                         @0
ub1 frmt_kcbh                         @1
ub1 spare1_kcbh                      @2
ub1 spare2_kcbh                      @3
ub4 rdba_kcbh                         @4
ub4 bas_kcbh                         @8
ub2 wrp_kcbh                         @12
ub1 seq_kcbh                         @14
ub1 flg_kcbh                         @15
ub2 chkval_kcbh                      @16
ub2 spare3_kcbh                      @18

struct ktbbh, 72 bytes                   @20
ub1 ktbbhtyp                         @20
union ktbbhsid, 4 bytes                @24
struct ktbbhcsc, 8 bytes             @28
sb2 ktbbhict                         @36
ub1 ktbbhflg                         @38
ub1 ktbbhfsl                         @39
ub4 ktbbhfnx                         @40
struct ktbbhitl[2], 48 bytes          @44

struct kdbh, 14 bytes                   @100
ub1 kdbhflag                         @100
sb1 kdbhntab                         @101
sb2 kdbhnrow                         @102
sb2 kdbhfrre                         @104
sb2 kdbhfsbo                         @106
sb2 kdbhfseo                         @108
sb2 kdbhavsp                         @110
sb2 kdbhtosp                         @112

struct kdbt[1], 4 bytes                   @114
sb2 kdbtoffs                         @114
sb2 kdbtnrow                         @116

sb2 kdbr[1]                               @118

ub1 freespace[8058]                      @120

ub1 rowdata[10]                         @8178

ub4 tailchk                               @8188

BBED> p chkval_kcbh
ub2 chkval_kcbh                            @16    0xd470

BBED> sum
Check value for File 12, Block 26243:
current = 0xd470, required = 0xd470

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

用dd命令导出12号文件
[oracle@orcl ~]$ dd if=/data/ORCL/datafile/hdb02.dbf of=/tmp/hdb1226243.dd count=1 skip=26243 bs=8192
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 0.00109806 s, 7.5 MB/s

用ue打开

dd if=/tmp/hdb1226243mod.dd of=/data/ORCL/datafile/hdb02.dbf seek=26243 bs=8192 count=1 conv=notrunc
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 0.000682266 s, 12.0 MB/s
[oracle@orcl tmp]$

SQL> startup
ORACLE instance started.

Total System Global Area 1252663296 bytes
Fixed Size       2252824 bytes
Variable Size    738201576 bytes
Database Buffers    503316480 bytes
Redo Buffers       8892416 bytes
Database mounted.
Database opened.
SQL>

SQL> select * from hdb12.test1;
select * from hdb12.test1
                  *
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 12, block # 26243)
ORA-01110: data file 12: '/data/ORCL/datafile/hdb02.dbf'

alert日志
Sun Jul 14 14:11:16 2019
Hex dump of (file 12, block 26243) in trace file /u01/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_5454.trc
Corrupt block relative dba: 0x03006683 (file 12, block 26243)
Bad check value found during multiblock buffer read
Data in bad block:
type: 6 format: 2 rdba: 0x03006683
last change scn: 0x0000.001aa310 seq: 0x1 flg: 0x06
spare1: 0x0 spare2: 0x0 spare3: 0x0
consistency value in tail: 0xa3100601
check value in block header: 0xd470
computed block checksum: 0x100
Reading datafile '/data/ORCL/datafile/hdb02.dbf' for corruption at rdba: 0x03006683 (file 12, block 26243)
Reread (file 12, block 26243) found same corrupt data (no logical check)
Sun Jul 14 14:11:17 2019
Corrupt Block Found
      TSN = 9, TSNAME = HDB_TBS
      RFN = 12, BLK = 26243, RDBA = 50357891
      OBJN = 91260, OBJD = 91260, OBJECT = TEST1, SUBOBJECT =
      SEGMENT OWNER = HDB12, SEGMENT TYPE = Table Segment
Corrupt Block Found
      TSN = 9, TSNAME = HDB_TBS
      RFN = 12, BLK = 26243, RDBA = 50357891
      OBJN = 91260, OBJD = 91260, OBJECT = TEST1, SUBOBJECT =
      SEGMENT OWNER = HDB12, SEGMENT TYPE = Table Segment
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_5454.trc  (incident=36154):
ORA-01578: ORACLE data block corrupted (file # 12, block # 26243)
ORA-01110: data file 12: '/data/ORCL/datafile/hdb02.dbf'
Incident details in: /u01/app/oracle/diag/rdbms/orcl/orcl/incident/incdir_36154/orcl_ora_5454_i36154.trc
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_5454.trc  (incident=36155):
ORA-01578: ORACLE data block corrupted (file # 12, block # 26243)
ORA-01110: data file 12: '/data/ORCL/datafile/hdb02.dbf'
Incident details in: /u01/app/oracle/diag/rdbms/orcl/orcl/incident/incdir_36155/orcl_ora_5454_i36155.trc
Sun Jul 14 14:11:20 2019
Dumping diagnostic data in directory=[cdmp_20190714141120], requested by (instance=1, osid=5454), summary=[incident=36154].
Sun Jul 14 14:11:21 2019
Sweep [inc][36154]: completed
Hex dump of (file 12, block 26243) in trace file /u01/app/oracle/diag/rdbms/orcl/orcl/incident/incdir_36154/orcl_m000_5488_i36154_a.tr
c
Corrupt block relative dba: 0x03006683 (file 12, block 26243)
Bad check value found during validation
Data in bad block:
type: 6 format: 2 rdba: 0x03006683
last change scn: 0x0000.001aa310 seq: 0x1 flg: 0x06
spare1: 0x0 spare2: 0x0 spare3: 0x0
consistency value in tail: 0xa3100601
check value in block header: 0xd470
computed block checksum: 0x100
Reread of blocknum=26243, file=/data/ORCL/datafile/hdb02.dbf. found same corrupt data
Reread of blocknum=26243, file=/data/ORCL/datafile/hdb02.dbf. found same corrupt data
Reread of blocknum=26243, file=/data/ORCL/datafile/hdb02.dbf. found same corrupt data
Reread of blocknum=26243, file=/data/ORCL/datafile/hdb02.dbf. found same corrupt data
Reread of blocknum=26243, file=/data/ORCL/datafile/hdb02.dbf. found same corrupt data
Dumping diagnostic data in directory=[cdmp_20190714141121], requested by (instance=1, osid=5454), summary=[incident=36155].
Checker run found 1 new persistent data failures
Sun Jul 14 14:11:48 2019
Sweep [inc][36155]: completed
Sweep [inc2][36155]: completed
Sweep [inc2][36154]: completed

check value in block header: 0xd470
computed block checksum: 0x100

重新计算checksum值，异或操作
d4 70  = 1101 0100 0111 0000
00 01  = 0000 0000 0000 0001
   = 1101 0100 0111 0001= d4 71

重新用bbed,修改
BBED> p chkval_kcbh
ub2 chkval_kcbh                            @16    0xd470

BBED> dump offset 16 count 32
File: /data/ORCL/datafile/hdb02.dbf (12)
Block: 26243          Offsets: 16 to 47          Dba:0x03006683
------------------------------------------------------------------------
70d40000 01000000 7c640100 0ea31a00 00000000 02003200 80660003 07000400

<32 bytes per line>
BBED> modify /x 71 offset 16
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /data/ORCL/datafile/hdb02.dbf (12)
Block: 26243          Offsets: 16 to 47          Dba:0x03006683
------------------------------------------------------------------------
71d40000 01000000 7c640100 0ea31a00 00000000 02003200 80660003 07000400

<32 bytes per line>

BBED> dump offset 16 count 32
File: /data/ORCL/datafile/hdb02.dbf (12)
Block: 26243          Offsets: 16 to 47          Dba:0x03006683
------------------------------------------------------------------------
71d40000 01000000 7c640100 0ea31a00 00000000 02003200 80660003 07000400

<32 bytes per line>

BBED> p chkval_kcbh
ub2 chkval_kcbh                            @16    0xd471

BBED> sum apply
Check value for File 12, Block 26243:
current = 0xd570, required = 0xd570

SQL> select * from hdb12.test1;

ID NAME
---------- ----------
   2 hdb