文件的文头是哪个位置

文件头是位于文件开头的一段承担一定任务的数据，一般都在开头的部分。头文件作为一种包含功能函数、数据接口声明的载体文件，用于保存程序的声明(declaration)，而定义文件用于保存程序的实现 (implementation)。

常见文件的文件头：

jpg: 255,216

gif: 71,73

bmp: 66,77

png: 137,80

doc: 208,207

docx: 80,75

xls: 208,207

xlsx: 80,75

js: 239,187

swf: 67,87

mp3: 73,68

wma: 48,38

mid: 77,84

rar: 82,97

zip: 80,75

xml: 60,63

在文件系统下用dd备份文件头部做测试

SQL>select name from v$datafile

NAME

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

/oradata/upgr/system01.dbf

/oradata/upgr/sysaux01.dbf

/oradata/upgr/undotbs01.dbf

/oradata/upgr/users01.dbf

SQL>

SQL>set lines 156 pages 100

SQL>col dd_backup_cmd for a156

SQL>col dd_restore_cmd for a156

SQL>select 'dd if='||name||' of=/backup/'||substr(name,instr(name,'/',-1)+1)||'.FH bs='||block_size||' count=2' dd_backup_cmd from v$datafile

DD_BACKUP_CMD

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

dd if=/oradata/upgr/system01.dbf of=/backup/system01.dbf.FH bs=8192 count=2

dd if=/oradata/upgr/sysaux01.dbf of=/backup/sysaux01.dbf.FH bs=8192 count=2

dd if=/oradata/upgr/undotbs01.dbf of=/backup/undotbs01.dbf.FH bs=8192 count=2

dd if=/oradata/upgr/users01.dbf of=/backup/users01.dbf.FH bs=8192 count=2

SQL>select 'dd of='||name||' if=/backup/'||substr(name,instr(name,'/',-1)+1)||'.FH bs='||block_size||' count=2 conv=notrunc' dd_restore_cmd from v$datafile

DD_RESTORE_CMD

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

dd of=/oradata/upgr/system01.dbf if=/backup/system01.dbf.FH bs=8192 count=2 conv=notrunc

dd of=/oradata/upgr/sysaux01.dbf if=/backup/sysaux01.dbf.FH bs=8192 count=2 conv=notrunc

dd of=/oradata/upgr/undotbs01.dbf if=/backup/undotbs01.dbf.FH bs=8192 count=2 conv=notrunc

dd of=/oradata/upgr/users01.dbf if=/backup/users01.dbf.FH bs=8192 count=2 conv=notrunc

SQL>

[oracle@db1 ~]$ dd if=/oradata/upgr/system01.dbf of=/backup/system01.dbf.FH bs=8192 count=2

2+0 records in

2+0 records out

16384 bytes (16 kB) copied, 0.000412654 s, 39.7 MB/s

破坏数据文件头部

[oracle@db1 ~]$ dd if=/dev/zero of=/oradata/upgr/system01.dbf bs=8192 count=2 conv=notrunc

2+0 records in

2+0 records out

16384 bytes (16 kB) copied, 0.000434433 s, 37.7 MB/s

[oracle@db1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Thu Jun 16 15:23:33 2016

Copyright (c) 1982, 2013, Oracle. All rights reserved.

Connected to an idle instance.

SQL>startup

ORACLE instance started.

Total System Global Area 313159680 bytes

Fixed Size 2252824 bytes

Variable Size 167776232 bytes

Database Buffers 138412032 bytes

Redo Buffers4718592 bytes

Database mounted.

ORA-01157: cannot identify/lock data file 1 - see DBWR trace file

ORA-01110: data file 1: '/oradata/upgr/system01.dbf'

SQL>shutdown abort

ORACLE instance shut down.

SQL>exit

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

With the Partitioning, Data Mining and Real Application Testing options

恢复数据文件头部

[oracle@db1 ~]$ dd of=/oradata/upgr/system01.dbf if=/backup/system01.dbf.FH bs=8192 count=2 conv=notrunc

2+0 records in

2+0 records out

16384 bytes (16 kB) copied, 0.000574576 s, 28.5 MB/s

[oracle@db1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Thu Jun 16 15:24:32 2016

Copyright (c) 1982, 2013, Oracle. All rights reserved.

Connected to an idle instance.

SQL>startup

ORACLE instance started.

Total System Global Area 313159680 bytes

Fixed Size 2252824 bytes

Variable Size 167776232 bytes

Database Buffers 138412032 bytes

Redo Buffers4718592 bytes

Database mounted.

Database opened.

SQL>exit

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

With the Partitioning, Data Mining and Real Application Testing options

[oracle@db1 ~]$

在ASM情况下用dd备份文件头部做测试

SQL>select ' dd '||

2 ' if=/backup/'||e.group_kffxp||'_'||e.disk_kffxp||'_'||a.file_number||'.FH'||

3 ' of='||d.path||

4 ' bs='||c.allocation_unit_size||

5 ' seek='||e.au_kffxp||

6 ' count=1 conv=notrunc' dd_restore_cmd

7 from

8 v$asm_alias a,

9 v$asm_file b,

10 v$asm_diskgroup c,

11 v$asm_disk d,

12 x$kffxp e

13 where a.file_number=e.number_kffxp

14and a.group_number=e.group_kffxp

15and b.group_number=a.group_number

16and d.group_number=c.group_number

17and e.group_kffxp=d.group_number

18and a.file_number=b.file_number

19and d.disk_number=e.disk_kffxp

20and a.system_created='Y'

21and b.type='DATAFILE'

22and e.xnum_kffxp=0

23order by a.file_number

24 /

DD_RESTORE_CMD

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

dd if=/backup/1_3_283.FH of=/dev/oracleasm/disks/ASMDISK7 bs=1048576 seek=21 count=1 conv=notrunc

dd if=/backup/1_4_285.FH of=/dev/oracleasm/disks/ASMDISK8 bs=1048576 seek=262 count=1 conv=notrunc

dd if=/backup/1_2_287.FH of=/dev/oracleasm/disks/ASMDISK6 bs=1048576 seek=266 count=1 conv=notrunc

dd if=/backup/1_1_288.FH of=/dev/oracleasm/disks/ASMDISK5 bs=1048576 seek=299 count=1 conv=notrunc

dd if=/backup/1_3_291.FH of=/dev/oracleasm/disks/ASMDISK7 bs=1048576 seek=163 count=1 conv=notrunc

SQL>

SQL>select ' dd'||

2 ' if='||d.path||

3 ' of=/backup/'||e.group_kffxp||'_'||e.disk_kffxp||'_'||a.file_number||'.FH'||

4 ' bs='||c.allocation_unit_size||

5 ' skip='||e.au_kffxp||

6 ' count=1' dd_backup_cmd

7 from

8 v$asm_alias a,

9 v$asm_file b,

10 v$asm_diskgroup c,

11 v$asm_disk d,

12 x$kffxp e

13 where a.file_number=e.number_kffxp

14and a.group_number=e.group_kffxp

15and b.group_number=a.group_number

16and d.group_number=c.group_number

17and e.group_kffxp=d.group_number

18and a.file_number=b.file_number

19and d.disk_number=e.disk_kffxp

20and a.system_created='Y'

21and b.type='DATAFILE'

22and e.xnum_kffxp=0

23order by a.file_number

24 /

DD_BACKUP_CMD

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

dd if=/dev/oracleasm/disks/ASMDISK7 of=/backup/1_3_283.FH bs=1048576 skip=21 count=1

dd if=/dev/oracleasm/disks/ASMDISK8 of=/backup/1_4_285.FH bs=1048576 skip=262 count=1

dd if=/dev/oracleasm/disks/ASMDISK6 of=/backup/1_2_287.FH bs=1048576 skip=266 count=1

dd if=/dev/oracleasm/disks/ASMDISK5 of=/backup/1_1_288.FH bs=1048576 skip=299 count=1

dd if=/dev/oracleasm/disks/ASMDISK7 of=/backup/1_3_291.FH bs=1048576 skip=163 count=1

SQL>

备份ASM中数据文件头部

[oracle@ohs1 ~]$ dd if=/dev/oracleasm/disks/ASMDISK7 of=/backup/1_3_283.FH bs=1048576 skip=21 count=1

1+0 records in

1+0 records out

1048576 bytes (1.0 MB) copied, 0.00664794 seconds, 158 MB/s

破坏ASM中数据文件头部

[oracle@ohs1 ~]$ dd if=/dev/zero of=/dev/oracleasm/disks/ASMDISK7 seek=21 count=1 conv=notrunc bs=1M

1+0 records in

1+0 records out

1048576 bytes (1.0 MB) copied, 0.000517497 seconds, 2.0 GB/s

[oracle@ohs1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Thu Jun 16 14:58:53 2016

Copyright (c) 1982, 2011, Oracle. All rights reserved.

Connected to an idle instance.

SQL>startup

ORACLE instance started.

Total System Global Area 318046208 bytes

Fixed Size 1344680 bytes

Variable Size 188746584 bytes

Database Buffers 121634816 bytes

Redo Buffers6320128 bytes

Database mounted.

ORA-01122: database file 1 failed verification check

ORA-01110: data file 1: '+DATA_PGOLD/racdb/system01.dbf'

ORA-01210: data file header is media corrupt

SQL>shut abort

ORACLE instance shut down.

SQL>exit

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production

With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,

Data Mining and Real Application Testing options

恢复ASM中数据文件头部

[oracle@ohs1 ~]$ dd if=/backup/1_3_283.FH of=/dev/oracleasm/disks/ASMDISK7 bs=1048576 seek=21 count=1 conv=notrunc

1+0 records in

1+0 records out

1048576 bytes (1.0 MB) copied, 0.00153561 seconds, 683 MB/s

[oracle@ohs1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Thu Jun 16 15:00:08 2016

Copyright (c) 1982, 2011, Oracle. All rights reserved.

Connected to an idle instance.

SQL>startup

ORACLE instance started.

Total System Global Area 318046208 bytes

Fixed Size 1344680 bytes

Variable Size 188746584 bytes

Database Buffers 121634816 bytes

Redo Buffers6320128 bytes

Database mounted.

Database opened.

SQL>select open_mode from v$database

OPEN_MODE

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

READ WRITE

SQL>

生成备份数据文件头部所需要的dd脚本(数据库用户)

set lines 156 pages 100

col dd_backup_cmd for a156

col dd_restore_cmd for a156

select 'dd if='||name||' of=/backup/'||substr(name,instr(name,'/',-1)+1)||'.FH bs='||block_size||' count=2' dd_backup_cmd from v$datafile

select 'dd of='||name||' if=/backup/'||substr(name,instr(name,'/',-1)+1)||'.FH bs='||block_size||' count=2 conv=notrunc' dd_restore_cmd from v$datafile

生成备份ASM数据文件头部所需要的dd脚本(在GI用户下ASM实例)

set lines 156 pages 100

col dd_backup_cmd for a156

col dd_restore_cmd for a156

select ' dd'||

' if='||d.path||

' of=/backup/'||e.group_kffxp||'_'||e.disk_kffxp||'_'||a.file_number||'.FH'||

' bs='||c.allocation_unit_size||

' skip='||e.au_kffxp||

' count=1' dd_backup_cmd

from

v$asm_alias a,

v$asm_file b,

v$asm_diskgroup c,

v$asm_disk d,

x$kffxp e

where a.file_number=e.number_kffxp

and a.group_number=e.group_kffxp

and b.group_number=a.group_number

and d.group_number=c.group_number

and e.group_kffxp=d.group_number

and a.file_number=b.file_number

and d.disk_number=e.disk_kffxp

and a.system_created='Y'

and b.type='DATAFILE'

and e.xnum_kffxp=0

order by a.file_number

/

select ' dd '||

' if=/backup/'||e.group_kffxp||'_'||e.disk_kffxp||'_'||a.file_number||'.FH'||

' of='||d.path||

' bs='||c.allocation_unit_size||

' seek='||e.au_kffxp||

' count=1 conv=notrunc' dd_restore_cmd

from

v$asm_alias a,

v$asm_file b,

v$asm_diskgroup c,

v$asm_disk d,

x$kffxp e

where a.file_number=e.number_kffxp

and a.group_number=e.group_kffxp

and b.group_number=a.group_number

and d.group_number=c.group_number

and e.group_kffxp=d.group_number

and a.file_number=b.file_number

and d.disk_number=e.disk_kffxp

and a.system_created='Y'

and b.type='DATAFILE'

and e.xnum_kffxp=0

order by a.file_number

/

生成备份ASM磁盘头部所需要的dd脚本(在GI用户下ASM实例)

set lines 150

set pages 1000

select

'dd if='||path||

' of=/backup/'||substr(path,instr(path,'/',-1)+1)||'_'||group_number||'_'||disk_number||'.DH bs=1M count=100'

from v$asm_disk asm_header_backup

where header_status='MEMBER'

order by group_number,disk_number

select 'dd if=/backup/'||substr(path,instr(path,'/',-1)+1)||'_'||group_number||'_'||disk_number||'.DH'||

' of='||path||' bs=1M count=100 conv=notrunc'

from v$asm_disk asm_header_restore

where header_status='MEMBER'

order by group_number,disk_number

生成asmcmd cp命令(数据库用户下执行)

select 'asmcmd cp '||name||' /backup/'||substr(name,instr(name,'/',-1)+1) asmcmd_cp from v$controlfile

union all

select 'asmcmd cp '||name||' /backup/'||substr(name,instr(name,'/',-1)+1) from v$datafile

union all

select 'asmcmd cp '||member||' /backup/'||thread#||'_'||a.group#||'_'||substr(member,instr(member,'/',-1)+1)

from v$log a, v$logfile b where a.group# = b.group#

ASMCMD_CP

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

asmcmd cp +DATA_PGOLD/racdb/control01.ctl /backup/control01.ctl

asmcmd cp +DATA_PGOLD/racdb/control02.ctl /backup/control02.ctl

asmcmd cp +DATA_PGOLD/racdb/system01.dbf /backup/system01.dbf

asmcmd cp +DATA_PGOLD/racdb/sysaux01.dbf /backup/sysaux01.dbf

asmcmd cp +DATA_PGOLD/racdb/undotbs01.dbf /backup/undotbs01.dbf

asmcmd cp +DATA_PGOLD/racdb/users01.dbf /backup/users01.dbf

asmcmd cp +DATA_PGOLD/racdb/undotbs02.dbf /backup/undotbs02.dbf

asmcmd cp +DATA_PGOLD/racdb/redo02.log /backup/1_2_redo02.log

asmcmd cp +DATA_PGOLD/racdb/redo01.log /backup/1_1_redo01.log

asmcmd cp +DATA_PGOLD/racdb/redo03.log /backup/2_3_redo03.log

asmcmd cp +DATA_PGOLD/racdb/redo04.log /backup/2_4_redo04.log

11 rows selected.

SQL>

然后执行以上命令即可

生成rman copy命令(数据库用户下执行)

select 'copy current controlfile to ''/tmp/'||substr(name,instr(name,'/',-1)+1)||'''' rman_copy from v$controlfile

union all

select 'copy datafile '||file#||' to ''/backup/'||substr(name,instr(name,'/',-1)+1)||'''' from v$datafile

RMAN_COPY

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

copy current controlfile to '/tmp/control01.ctl'

copy current controlfile to '/tmp/control02.ctl'

copy datafile 1 to '/backup/system01.dbf'

copy datafile 2 to '/backup/sysaux01.dbf'

copy datafile 3 to '/backup/undotbs01.dbf'

copy datafile 4 to '/backup/users01.dbf'

copy datafile 5 to '/backup/undotbs02.dbf'

7 rows selected.

SQL>

然后使用rman这些以上命令

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