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Posted to derby-user@db.apache.org by Mojo Nixon <st...@gmail.com> on 2012/01/27 15:47:10 UTC

Really Strange Database Corruption. Help!

I recently received a database from a user. They said they were viewing a
record in the application, and went back to open it a bit later and the
record was gone. In the database the record is indeed gone, but when I look
at the table .dat file in a binary editor, I can see the record information! 

So I have the following questions: 
 - How could this happen? The table is corrupt, but the database continues
to function? 
 - Is there any way to get the record back? 
 - Are there any derby tools for this sort of forensic recovery of records,
like some low level tools that can read and dump what is in a single dat
file? 
 - Could it just be an issue of the record being deleted? They insist they
did not, but you know users... 

Thanks for any advice. 
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Re: Really Strange Database Corruption. Help!

Posted by Rick Hillegas <ri...@oracle.com>.

On 1/27/12 6:47 AM, Mojo Nixon wrote:
> I recently received a database from a user. They said they were viewing a
> record in the application, and went back to open it a bit later and the
> record was gone. In the database the record is indeed gone, but when I look
> at the table .dat file in a binary editor, I can see the record information!
>
> So I have the following questions:
>   - How could this happen? The table is corrupt, but the database continues
> to function?
>   - Is there any way to get the record back?
>   - Are there any derby tools for this sort of forensic recovery of records,
> like some low level tools that can read and dump what is in a single dat
> file?
The DataFileReader attached to 
https://issues.apache.org/jira/browse/DERBY-5201 may help.

Hope this is useful,
-Rick
>   - Could it just be an issue of the record being deleted? They insist they
> did not, but you know users...
>
> Thanks for any advice.