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Database corrupt after FTP (on some computers)

P: n/a

I'm a little stumped here, and it might be beyond the scope of this
forum - but any help would be greatly appreciated.

I have a database being used across remote offices with no network, so
I'm using a system of FTP routines and a lock file to allow the users
to do updates and get and put the latest database backend using FTP to
a secure web server.

Sounds a little funky, but the system actually works great - on some
computers - but in two cases, for no appearent reason the database is
corrupted after download.

DB Version: Access 2000
Filesize: backend ~2MB, FE ~4MB
No limit on FTP server re filesize
Transfer done in ASCII mode (Binary corrupts every time on every
PC...)
Webserver is Linux
Practically every PC is differnet Specs, windows SP versions etc
Interestingly, the two it won't work on are both fairly new laptops
I dont think its an ISP thing, because for two computers on the same
internet connection, one works and the other doesnt

Anyone have any clue at all?

Mar 5 '07 #1
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3 Replies


P: n/a
I would STRONGLY suggest that you consider zipping the files before you
transfer.

FTP does fail quite often, and unless you having something that checks for
errors in the file...you setup is to risky...

I have a WinZip compatible library that you could use. You can find it here:

http://www.members.shaw.ca/AlbertKallal/zip/index.htm
Sounds a little funky, but the system actually works great - on some
computers - but in two cases, for no appearent reason the database is
corrupted after download.
It sounds quite a bit funky, and your problems demonstrate that this is not
a reliable setup.

I suspect that the computers in which this is occurring are actually
correctly doing a ASCII mode. You MUST USE binary transfer
mode here.

Binary mode should not be corrupting every time. Binary means to
transfer the data un-modified. ASCII mode means to convert
char returns..and other things on the fly. So, with ASCII
mode, you doing a text transfer, but you document is MOST
CERTAINLY binary data format. You have to fix this issue
first....

Or, as mentioned, using something that wraps the file in some type of error
checking. I would start with the WinZip idea, and the bonus that your file
sizes will be 2 times, or more smaller. It is news to me that you can
transfer a binary file, or a zip file while in ASCII mode. For transferring
of any type of compressed data (which access 2000 and onward uses), I just
can't imagine that non binary transfers will work. I am more perplexed that
whole thing actually works. I would try transferring a zip file...and if
that works, then grab the above zip examples, as at least that would improve
your reliability.

My fear/concern here is that you doing a ASCII transfer, but in fact data is
being changed, or last VERY frequently...you just don't notice...

I am rather surprised that this works, and you need more robust error
checing for you data, as FTP is not at all that great. And, you need to get
the binary transfers working...

--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pl*****************@msn.com
Mar 5 '07 #2

P: n/a

I agree with the whole ACSII Vs Binary thing - I was initially using
Binary...
Thanks for the advice the and ZIP dlls. I'll take your advice and look
into this.

On Mar 5, 4:37 pm, "Albert D. Kallal" <PleaseNOOOsPAMmkal...@msn.com>
wrote:
I would STRONGLY suggest that you consider zipping the files before you
transfer.

FTP does fail quite often, and unless you having something that checks for
errors in the file...you setup is to risky...

I have a WinZip compatible library that you could use. You can find it here:

http://www.members.shaw.ca/AlbertKallal/zip/index.htm
Sounds a little funky, but the system actually works great - on some
computers - but in two cases, for no appearent reason the database is
corrupted after download.

It sounds quite a bit funky, and your problems demonstrate that this is not
a reliable setup.

I suspect that the computers in which this is occurring are actually
correctly doing a ASCII mode. You MUST USE binary transfer
mode here.

Binary mode should not be corrupting every time. Binary means to
transfer the data un-modified. ASCII mode means to convert
char returns..and other things on the fly. So, with ASCII
mode, you doing a text transfer, but you document is MOST
CERTAINLY binary data format. You have to fix this issue
first....

Or, as mentioned, using something that wraps the file in some type of error
checking. I would start with the WinZip idea, and the bonus that your file
sizes will be 2 times, or more smaller. It is news to me that you can
transfer a binary file, or a zip file while in ASCII mode. For transferring
of any type of compressed data (which access 2000 and onward uses), I just
can't imagine that non binary transfers will work. I am more perplexed that
whole thing actually works. I would try transferring a zip file...and if
that works, then grab the above zip examples, as at least that would improve
your reliability.

My fear/concern here is that you doing a ASCII transfer, but in fact data is
being changed, or last VERY frequently...you just don't notice...

I am rather surprised that this works, and you need more robust error
checing for you data, as FTP is not at all that great. And, you need to get
the binary transfers working...

--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOOSpamKal...@msn.com

Mar 6 '07 #3

P: n/a

You're a legend - zip dlls and code works a storm - thank you so
much!!!

I've traced my problems to some dodgy ftp coding, I was trying to use
an ftp class using API so that I could trap errors, but it seems the
code is buggy - ASCII Vs Binary connections are a little skewed.

So the solution I'm going to use is to do the ftp work via temporary
batch files and parse the dos output to do my error checking.

In case you are interrested, I'll let you know how I get on

Thanks a million for your help

Bill

Mar 13 '07 #4

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