At 09:38 PM 4/26/00 +1000, Helen Borrie wrote:

>I've had several people suggest a topic for the IBDH along the lines of...
>
>"We need a topic that describes the structure of the database so that I can
>open the .gdb with a suitable editor and retrieve good data from a corrupt
>database."
>
>In my high-handed way, I've tended just to say to myself "Pooph! another
>of THOSE!" I've always assumed (rightly or wrongly) that it would be like
>looking for a needle in a haystack, given the relative randomness of
>storage of rows, never mind tables, indexes, etc.
>
>But - is there any way?

Most of the Interbase structural linkage has redundancy that should
make it possible to build a tool that reconstructs most of a corrupt
database. For example, data pages are normally located through a
"pages" page. However, each data page also carries the id of the table
it belongs to and its sequence number within the table. If a "pages"
page is lost, one could rebuild it.

If you lost a primary record version, for example, you couldn't
retrieve the back versions if they were stored in "diff" form.
You could, however, read a back version that was stored in its
complete form, e.g. one that sits behind a deleted record.

Obviously all the structural definitions to produce such a tool
will be available.


This makes a fascinating contrast with the security discussions going
on elsewhere.

Ann

Cheers,

Ann