Data corruption

[Bill Campbell]

On Tue, Dec 11, 2007, Fairlight wrote:
>Only Don Coleman would say something like:
>> Client had a hard drive fail over the weekend.  I have identified some data
>> corruption in an archive file at this point.  Most of the corrupted records
>> are in small batches of 20-50 records although a few are single individual
>> records.  I am unable to delete the corrupted records (nothing happens on
>> the screen).  Is there any way to get rid of these?  The hard drive failed
>> during the backup and I can piece the data together if I can eliminate the
>> corrupted records.
>> 
>> Windows 2003 server, fPv5.0.13, WIN2000 & WINXP Pro clients.
>
>Shouldn't it be possible to write a program that takes the record length
>and tries to get a record at every [offset] bytes, and reject the bad ones
>based on some (as yet undefined) criterion?  Then just rebuild the indexes?

I ran into a problem about 20 years ago on a Tandy Xenix system where the
key/data files had problems as the data had been shifted left or right at
various places in the files.

Fixing this involved writing a C program that would read and copy the files
to a specified record number, shift left or right a bit using lseek, then
continue copying.  This was an interative process as one had to view the
records one at a time until a shift was detected, mark the record number,
and the number of bytes shifted, run the program again with these options,
rinse repeat until the files were clean.

Bill
--
INTERNET:   bill at celestial.com  Bill Campbell; Celestial Software LLC
URL: http://www.celestial.com/  PO Box 820; 6641 E. Mercer Way
FAX:            (206) 232-9186  Mercer Island, WA 98040-0820; (206) 236-1676

The day-to-day travails of the IBM programmer are so amusing to most of
us who are fortunate enough never to have been one -- like watching
Charlie Chaplin trying to cook a shoe.