We have 100s of installation of a desktop application that uses DBISAM engine (mostly
v4.23). In the past few weeks we got 4 reports about corrupt database. After looking
closely at 2 cases we figured out that one of our tables was missing few files.

We expect to have

BucketItem.bbk
BucketItem.blb
BucketItem.dat
BucketItem.dbk
BucketItem.ibk
BucketItem.idx

But on the corrupt systems we have

BucketItem.dat
BucketItem.idx

Our observations

1. On both systems we have exactly the same 4 files missing. Only IDX and DAT files were
left untouched.
2. This table is the only table where we delete records actively

Questions

1. Has anybody experienced similar db corruption?
2. Is there anything special about name "BucketItem" ?
3. Is there anything special about deleting all records from the table?

Thank you

I noticed that on default installation we have 3 files

BucketItem.blb
BucketItem.dat
BucketItem.idx

Which means that on "corrupt" systems we have BLB file missing

"alex u" <alex@zfirmllc.com> wrote in message
news:6238A0DB-66F2-4D9B-A2D7-02A104801E8B@news.elevatesoft.com...
> We have 100s of installation of a desktop application that uses DBISAM
> engine (mostly
> v4.23). In the past few weeks we got 4 reports about corrupt database.
> After looking
> closely at 2 cases we figured out that one of our tables was missing few
> files.
>

the xxx.xBK files are bakup files created by operations such as a table
restructure. Is it possible someone tried to delete them and ended up
deleting also the blb (blob) file? Ot maybe you have some code in your
program that is doing the delete, tsk tsk?

Robert

> We expect to have
>
> BucketItem.bbk
> BucketItem.blb
> BucketItem.dat
> BucketItem.dbk
> BucketItem.ibk
> BucketItem.idx
>
> But on the corrupt systems we have
>
> BucketItem.dat
> BucketItem.idx
>
> Our observations
>
> 1. On both systems we have exactly the same 4 files missing. Only IDX and
> DAT files were
> left untouched.
> 2. This table is the only table where we delete records actively
>
> Questions
>
> 1. Has anybody experienced similar db corruption?
> 2. Is there anything special about name "BucketItem" ?
> 3. Is there anything special about deleting all records from the table?
>
> Thank you
>

>the xxx.xBK files are bakup files created by operations such as a table
>restructure. Is it possible someone tried to delete them and ended up
>deleting also the blb (blob) file? Ot maybe you have some code in your
>program that is doing the delete, tsk tsk?

We already looked at our code. There are no explicit "delete file" or "delete table"
calls. Also if we had explicit "delete file" code we would expect much higher % of users
reporting this issue.

Another thing - we had no reports of this kind for more then an year and now we had 5
incidents in 2 weeks. Very strange....

Alex,

> We have 100s of installation of a desktop application that uses DBISAM
> engine (mostly
> v4.23). In the past few weeks we got 4 reports about corrupt database.
> After looking
> closely at 2 cases we figured out that one of our tables was missing few
> files.
>
> [snip]
>
> 1. Has anybody experienced similar db corruption?

Yes. We have had a significant increase in the last couple of months of
problems where database files are deleted or they are truncated to zero
bytes.  This is with both 4.24b1 and the latest build of 4.26.

Unfortunately I have not been able to track down any commonality between the
locations that have the problem compared to the hundreds of installations
that are running without any problems.  Originally we thought that it was
anti-virus software, but we've seen this on a few systems without anit-virus
software installed.  The only thing that I know for sure is that the problem
appears to be restricted to local database connections as I have not had any
reports of this from customers running a client/server configuration.

I know this probably doesn't help much, but at least you know you are not
alone.

--

---------------------------------------
 Terry Swiers
 Millennium Software, LLC
 http://www.1000years.com
 http://www.atrex.com

 Email: mailto:support@atrex.com
---------------------------------------

We also had this problem whith one customer: the several .blb files where
missing.
delphi 7, dbisam version 4.24 build 1

Erik


"Terry Swiers" <millennium@1000years.com> schreef in bericht
news:D45D9AB7-5DA9-43B0-8884-9E08930FAEE5@news.elevatesoft.com...
> Alex,
>
>> We have 100s of installation of a desktop application that uses DBISAM
>> engine (mostly
>> v4.23). In the past few weeks we got 4 reports about corrupt database.
>> After looking
>> closely at 2 cases we figured out that one of our tables was missing few
>> files.
>>
>> [snip]
>>
>> 1. Has anybody experienced similar db corruption?
>
> Yes. We have had a significant increase in the last couple of months of
> problems where database files are deleted or they are truncated to zero
> bytes.  This is with both 4.24b1 and the latest build of 4.26.
>
> Unfortunately I have not been able to track down any commonality between
> the
> locations that have the problem compared to the hundreds of installations
> that are running without any problems.  Originally we thought that it was
> anti-virus software, but we've seen this on a few systems without
> anit-virus
> software installed.  The only thing that I know for sure is that the
> problem
> appears to be restricted to local database connections as I have not had
> any
> reports of this from customers running a client/server configuration.
>
> I know this probably doesn't help much, but at least you know you are not
> alone.
>
> --
>
> ---------------------------------------
>  Terry Swiers
>  Millennium Software, LLC
>  http://www.1000years.com
>  http://www.atrex.com
>
>  Email: mailto:support@atrex.com
> ---------------------------------------
>
>
>
>

OK, so we have at least 3 companies reporting missing BLBs....

I am wondering if there is a new version of Norton Antivirus or something like was
released recently that deletes BLB files

Elevate guys
 - is there any way for us to rename BLB to something else?
 - can you start your internal investigation, since it will probably affect more of your
customers ?

Alex,

<< OK, so we have at least 3 companies reporting missing BLBs....

I am wondering if there is a new version of Norton Antivirus or something
like was released recently that deletes BLB files >>

It's certainly possible and I wouldn't be surprised if it was AV software.
Did you verify whether the customer was using AV software or not ?

<< - is there any way for us to rename BLB to something else? >>

Sure, see here:

http://www.elevatesoft.com/dbisam4d7_customizing_engine.htm

under "File Extension Customizations".

<< - can you start your internal investigation, since it will probably
affect more of your customers ? >>

There's not much I can do other than to verify whether DBISAM is the cause,
and I can assure you that it is not randomly deleting .BLB files.  If it is
indeed AV software or something else external, there really is no way for me
to verify this without first knowing exactly what the environment is in
which it is occurring.

--
Tim Young
Elevate Software
www.elevatesoft.com

Terry,

<< Yes. We have had a significant increase in the last couple of months of
problems where database files are deleted or they are truncated to zero
bytes.  This is with both 4.24b1 and the latest build of 4.26. >>

The only issue with truncation was discussed here, and it only applies to
corrupted .IDX files that have a size that is less than the expected index
header size, therefore making them unusable anyways:

http://www.elevatesoft.com/scripts/newsgrp.dll?action=openmsg&group=5&msg=58604&page=1#msg58604

..DAT and .BLB files are not handled in this way and DBISAM simply attempts
to open them.  If they do not exist, then something external to DBISAM
deleted them.


--
Tim Young
Elevate Software
www.elevatesoft.com

We have a customer where BLB get deleted daily. Setting up FileMon to see who is
responsible... Stay tuned...