Re: Data integrity

From: BP Margolin (bpmargo_at_attglobal.net)
Date: 05/12/03 

Date: Mon, 12 May 2003 05:21:22 -0400

Christian,

The physical database files contain both data and metadata. If the bit that you change is metadata, you might very well end up with a corrupted database. If the bit that you change is data, then to some extent the question becomes "What is SQL Server doing at the moment that the bit changes?".

For example, SQL Server could have read the data from the physical medium a moment before you changed the bit, and then be about to write back to the physical medium new data. In this sequence, the bit change you made is going to be "invisible" because the changed bit is going to be overwritten without being used.

Of course, much more likely, if you change a bit, then the next time that SQL Server reads the bit, it's going to just read the changed bit, and not know that it has changed.

> If there is no internal security mechanism in SQL server I
> have to implement crc or hash algorithms for any data
> storing in my application.

> I need it for certification of a product which is used in
> a medical product which claims for 100% data integrity.

I don't mean to be difficult, but even the use of crc or hash algorithms do not guarantee 100% data integrity. In fact, NOTHING guarantees 100% data integrity. It just ain't possible in the real world ... you can get very, very close to 100%, but you can never actually there. As an analogy ... both fingerprints and DNA is acceptable legal evidence at least in the USA to "uniquely" identify an individual. Problem there is, if you read the scientific literature carefully, neither fingerprints nor DNA are actually 100% "safe" in that regards. There is a very, very, very low probability of two people having the same fingerprints, but the probability just ain't zero. With DNA, the easiest counterexample are identical twins :-)

-------------------------------------------
BP Margolin
Please reply only to the newsgroups.
When posting, inclusion of SQL (CREATE TABLE ..., INSERT ..., etc.) which
can be cut and pasted into Query Analyzer is appreciated.

"Christian Rosenzweig" <Christian.Rosenzweig@medvision.de> wrote in message news:02d301c3185e$fc189dd0$a301280a@phx.gbl...
> Hallo,
>
> when I change any bit in the database (e.g. by hex editor)
> or any bit changes by physical effects like magnetism what
> happens with my SQL server? Does it recognize such
> manipulations? Is there a warning? Or do I get wrong data
> according to changed bits?
>
> Microsoft seems to refuse to give me a official statement.
> I need it for certification of a product which is used in
> a medical product which claims for 100% data integrity.
>
> If there is no internal security mechanism in SQL server I
> have to implement crc or hash algorithms for any data
> storing in my application.
>
> Thanks for any helpful answers.

Relevant Pages

  • Data integrity
    ... or any bit changes by physical effects like magnetism what ... a medical product which claims for 100% data integrity. ... If there is no internal security mechanism in SQL server I ...
    (microsoft.public.sqlserver.security)
  • Re: Data integrity
    ... To the best of my knowledge, SQL Server does not offer the level of data integrity that might be required by your application. ... > mechanisms in the database and I have to use fingerprints ...
    (microsoft.public.sqlserver.security)
  • Re: code Sample
    ... The MAJOR thing wrong with the below link is that it makes NO reference to ... only references the storing of images, such as *.jpg files (which can also ... Search that is fully support by Microsoft in SQL Server 7.0, ... > The following article and links to KB articles should give you everything ...
    (microsoft.public.sqlserver.programming)
  • Re: Store Multi-Select values in an image data type?
    ... SQL Server reports as the column width for text/ntext/image columns. ... >> storing the multiple selection choices I was doing through the app. ... >> data type colum with the variable length of 26 bytes. ...
    (comp.databases.ms-sqlserver)
  • Re: Linking table without duplicating PK
    ... applications can share safely share the same database. ... security in Access/Jet is inadequate for the required task. ... excellent, even in the free versions (MSDE 2000, SQL Server 2005 ... Data integrity is also an important and will be more easily achieved if ...
    (microsoft.public.access.tablesdbdesign)