Re: SQL Err when WLAN conn is dropped and then restored. Help!
From: Mystic Mong (alastair.williamson_at_tiso.co.uk)
Date: 08/17/04
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Date: Tue, 17 Aug 2004 22:22:04 +0100
Hi Callon,
We run ppc's in our warehouse that communicate via wireless lan with our SQL
Server 2000 database. We have a wireless black spot in one area of the
warehouse where the signal strength gets really low and the units sometimes
lose their wireless connection. I had some trouble initially that was
similar to the problem you are experiencing - the software was trapping
errors whilst in the black spot but the errors continued when the units
moved back into wireless range. One thing I found was that the sql
connection was failing when the signal strength was below 25%, I guess the
signal is just not strong enough. Another problem was that the units were
taking a bit of time to pick up their DHCP address when they were back in
range - everything was more reliable when the units were Static IP but this
was a pain so we went back to DHCP. The only problem from a coding point of
view was that I made absolutely sure that every reference to the sql
connection is disposed as soon as possible after each push/pull of data. I
changed the code so that the connection object (and every command, data
adapter, data reader etc) is defined within each procedure and disposed
within each procedure (again a bit of a pain because it vastly increases the
length of the code) we have not had any problems. The units go in and out of
our wireless black spot and the problem does not exist any more.
I realise that this is not exactly a "solution" to your problem but if you
are sure that your code shouldn't really be affected by any wireless
down-time then I suggest you look carefully at what happens to your units
when this happens and any network or server issues that may be raised.
Best of luck
C-Ya Aly
"Callon Campbell" <Callon Campbell@discussions.microsoft.com> wrote in
message news:E856C2AA-D9D1-4A5B-8D3A-00974069BF5B@microsoft.com...
> Hi,
>
> I've developed a CF application that communicates to a backend SQL Server
> 2000 DB over a WLAN. It is working fine, but occasionally the wireless PPC
> looses it;s connection while the application is running. the next time a
user
> goes to hit the SQL DB (note: everytime a user goes to the SQL server, an
> SqlConnection object is created and opened. I then close it when my data
has
> come back and I'm done using it), I get an error saying the DB doesn't
exist.
> If I quit the application and re-start it will work fine.
>
> What would be causing this problem (not the dropping of the WLAN, but the
> error occuring AFTER the connection to the WLAN is restored and the user
goes
> to communicate to the DB)?
>
> Any help would be greatly appreciated. I can send sample code of one of my
> functions for reference if need be. Just send me an email and I'll reply
back.
>
> Thanks in advance
>
> Cheers,
> Callon
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