COPYING RAW DEVICE TO FILE SYSTEM USING DD COMMAND

1.raw to fs(数据文件的大小需要为oracle blocksize的整数倍)

 

$ dd if=/dev/rUSERS_1024M of=/oracle/users.dbf skip=1 bs=4096 count=262142
262142+0 records in.
262142+0 records out.

 

2.fs to raw(数据文件的大小需要为oracle blocksize的整数倍)

$ dd if=/oracle/users.dbf of=/dev/rUSERS_1024M seek=1 bs=4096 count=262142
262142+0 records in.
262142+0 records out.

 

AIX: COPYING RAW DEVICE TO FILE SYSTEM USING DD COMMAND [ID 1027958.6]
		Modified 13-AUG-2008     Type PROBLEM     Status PUBLISHED

Problem Description: 
====================== 
How to backup the database on the raw device to the filesystem using 'dd'.



 
 
Solution Description: 
===================== 
 
The following commands will allow you to copy a raw device to the filesystem 
and restore from the filesystem to the raw device. 
 
You must use the dd command to copy from the raw device.  
 
Please Note: 
============  
	1. Caution is required because some AIX backup programs ignore large 
	files; you must	verify that any oversized AIX files are indeed  
        backed up.	  
  
	2. When doing copy/backup operations, please consider the 4KB 
	offset (taken by Oracle) for the Logical Volume Control Block(LVCB) at 
	the beginning of all IBM Virtual Shared Disks when performing 
	backup/restore operations. 
        
        3. When using zero offset raw devices (devices created using:
        # mklv -T O -y new_raw_device VolumeGroup NumberOfPartitions), ensure
        the 'skip' parameter is adjusted accordingly.  The offset can be 4096 
        bytes or 128 KB on AIX logical volumes or zero on AIX logical volumes 
        created with the mklv -T O option.
 
Copying to Filesystem  
--------------------------  
  
Use the command:  
  
% dd if= of= bs= 
skip= 
  
Example:  
% dd if=/dev/rVh09.za.716c1 of=/a/spdevs04/ibmfs/osupport/dismith/test.ctl 
bs=4096 skip=1 
 
In the above example we specify the blocksize as 4096 bytes and skip 1 block 
for the offset for the Logical Volume Control Block(LVCB) 
 
bs=BlockSize - Specifies both the input and output block size, 
superceding the ibs and obs flags. The block size values specified with 
the bs flag must always be a multiple of the physical block size for the 
media being used. 
 
skip=SkipInputBlocks - Skips the specified SkipInputBlocks value of 
input blocks before starting to copy. 
 
Restoring from Filesystem  
--------------------------  
 
Use the command:  
  
% dd if=/a/spdevs04/ibmfs/osupport/dismith/test.ctl of=/dev/rVh09.za.716c1 
bs=4096 seek=1  
 
In the above example we specify the blocksize as 4096bytes and seek 1 block 
past the beginning of output file before copying, so we will not 
overwrite the Logical Volume Control Block(LVCB) 
 
seek=RecordNumber - Seeks the record specified by the RecordNumber  
variable from the beginning of output file before copying.