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Data integrity

5 posts in General Discussion Last posting was on 2003-04-29 16:34:21.0Z
Christian Rosenzweig Posted on 2003-04-28 14:31:39.0Z
From: "Christian Rosenzweig" <Christian.Rosenzweig@medvision.de>
Subject: Data integrity
Date: Mon, 28 Apr 2003 16:31:39 +0200
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Article PK: 3327

Hi,
I am new with sybase and I have following question:
What machanisms in the Anywhere Adaptive Server are responsible for ensuring
data integrity?
For example if I change any byte in the database file by hex editor does the
db recognize this? How?
Where do I get reliable information about this? The hotline could not help
me, perhaps anybody here knows it.
Thanks a lot!


Jason Hinsperger Posted on 2003-04-28 14:43:32.0Z
From: "Jason Hinsperger" <NOJason_HinspergerSPAM@hotmail.com>
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Subject: Re: Data integrity
Date: Mon, 28 Apr 2003 10:43:32 -0400
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Article PK: 2956

If you use a hex editor to alter a random byte in the database file, several
things could happen:
1) If you modify an used protion of the database (eg. a free page), nothing
will happen.
2) If you modify data, but the result is still valid data for the column's
data type, the data will be changed, but unless the data was part of a key
or index, nothing will happen. If the data was a part of a key or index,
you have effecticely corrupted the database, which would be detected when
the server tries to access that data (possibly by an asertion, possibly by
returning incorrect query results) or when you validate the database using
the dbvalid utility.
3) If you alter system data, or data that defines the layout of the
database, the engine will fail start, crash or assert, depending on what you
have altered.

This is all I could think of off the top of my head, there may be more.

That said, using a hex editor to change a file is likely to wreak havoc with
any database vendors software, rendering the database unusable. This should
not be a concern for you if you adequately protect access to the database
file itself, and have an adequate backup and recovery strategy in place. I
would recommend reading the help chapters on backup and recovery for more
details.

--
Jason Hinsperger
International and Sustaining Engineering
iAnywhere Solutions

Whitepapers, TechDocs, and bug fixes are all available through the iAnywhere
Developer Community at www.ianywhere.com/developer
--

"Christian Rosenzweig" <Christian.Rosenzweig@medvision.de> wrote in message
news:#LyzONZDDHA.220@forums-1-dub...
> Hi,
> I am new with sybase and I have following question:
> What machanisms in the Anywhere Adaptive Server are responsible for
ensuring
> data integrity?
> For example if I change any byte in the database file by hex editor does
the
> db recognize this? How?
> Where do I get reliable information about this? The hotline could not help
> me, perhaps anybody here knows it.
> Thanks a lot!
>
>


Paul Horan[TeamSybase] Posted on 2003-04-28 16:52:53.0Z
From: "Paul Horan[TeamSybase]" <paulhATvcisolutionsDOTcom>
References: <#LyzONZDDHA.220@forums-1-dub> <O7jQSVZDDHA.196@forums-2-dub>
Subject: Re: Data integrity
Date: Mon, 28 Apr 2003 12:52:53 -0400
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Article PK: 3328

>>For example if I change any byte in the database file by hex editor does
the db recognize this?<<

That's like asking "If I put a loaded gun to my forehead and pull the
trigger, what security mechanisms has the gun manufacturer built in to
prevent my untimely death?"...

--
Paul Horan[TeamSybase]
VCI Springfield, MA
www.vcisolutions.com

Join the PB9 Book mailing list!
www.pb9book.com


Jason Hinsperger Posted on 2003-04-28 19:15:58.0Z
From: "Jason Hinsperger" <NOJason_HinspergerSPAM@hotmail.com>
References: <#LyzONZDDHA.220@forums-1-dub> <O7jQSVZDDHA.196@forums-2-dub> <ejLwkdaDDHA.194@forums-2-dub>
Subject: Re: Data integrity
Date: Mon, 28 Apr 2003 15:15:58 -0400
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Article PK: 3329

Nice analogy. I wish I could have thought of it...<g>

--
Jason Hinsperger
International and Sustaining Engineering
iAnywhere Solutions

Whitepapers, TechDocs, and bug fixes are all available through the iAnywhere
Developer Community at www.ianywhere.com/developer
--

"Paul Horan[TeamSybase]" <paulhATvcisolutionsDOTcom> wrote in message
news:ejLwkdaDDHA.194@forums-2-dub...
> >>For example if I change any byte in the database file by hex editor does
> the db recognize this?<<
>
> That's like asking "If I put a loaded gun to my forehead and pull the
> trigger, what security mechanisms has the gun manufacturer built in to
> prevent my untimely death?"...
>
> --
> Paul Horan[TeamSybase]
> VCI Springfield, MA
> www.vcisolutions.com
>
> Join the PB9 Book mailing list!
> www.pb9book.com
>
>


Graeme Perrow Posted on 2003-04-29 16:34:21.0Z
From: "Graeme Perrow" <gperrowNO@SPAMianywhere.com>
References: <#LyzONZDDHA.220@forums-1-dub> <O7jQSVZDDHA.196@forums-2-dub> <ejLwkdaDDHA.194@forums-2-dub>
Subject: Re: Data integrity
Date: Tue, 29 Apr 2003 12:34:21 -0400
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Article PK: 3331

Obviously this is a bad thing to do, but I think the OP was asking if the
server would detect the change and give some kind of "database file is
corrupt" message. The answer there is no.

--
Graeme Perrow
gperrow@ianywhere.com
iAnywhere Solutions, Inc.
A Sybase company

"Paul Horan[TeamSybase]" <paulhATvcisolutionsDOTcom> wrote in message
news:ejLwkdaDDHA.194@forums-2-dub...
> >>For example if I change any byte in the database file by hex editor does
> the db recognize this?<<
>
> That's like asking "If I put a loaded gun to my forehead and pull the
> trigger, what security mechanisms has the gun manufacturer built in to
> prevent my untimely death?"...
>
> --
> Paul Horan[TeamSybase]
> VCI Springfield, MA
> www.vcisolutions.com
>
> Join the PB9 Book mailing list!
> www.pb9book.com
>
>