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How to Dump or Extract a Raw Block From a File Stored in an ASM Diskgroup (Doc ID 603962.1)

Last updated on AUGUST 04, 2018

Applies to:

Oracle Database - Enterprise Edition - Version and later
Information in this document applies to any platform.


To provide a simple mechanism to extract a particular block from a datafile stored in an ASM diskgroup. 

When database files are stored in file systems or raw devices, it is possible to use dd command to extract the particular block from the particular file.

$ dd if=<file name> of=<new file> bs=<block_size> skip=<block of interest> count=1

When database files are stored in ASM, this is not possible because external tools like dd command can not be execute directly on the ASM files.  In addition, in order to extract the block using dd command, is required to identify the specific location on the disk where  the block  is located.  This requires running extra steps that make the procedure complex and exposed to errors.

The procedure can be used to extract blocks from any file stored in ASM.


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