Loosing connection?

[geralf]

Hi!

I'm running a split MS Access database. Backend at the server and front end at each workstation.

Now we want to use the database on a laptop with a wireless LAN adapter. The laptop will be placed in a loading vehicle which drives all over the company's site. When the laptop looses it's connection to the network, this will (I think) create an error (and the database stops working). If this is so, how can I solve such a problem?

Thanks in advance.

 

[WayneRyan]

geralf,

Don't have any experience in this arena, but I have a few comments.
Access REALLY doesn't like people suddenly disconnecting themselves
during a session. That usually leads to a wide variety of errors
such as locked/corrupted ".ldb" files. Not necessarily a loss of data,
but a penalty in maintaining the database environment.

There appears to be a very high probability that network service
can terminate at any second. To me, the first thing to do is
restrict database connections to as short a time as possible.
This could actually be a situation where unbound forms could be
useful. Your only network traffic would be through ODBC and wouldn't
have the constant saving activity of Access.

Just some thoughts, it'd be interesting to hear some facts/figures
for expected down-time %. And when you start out, post back here
about how Access handles it.

Wayne

 

[geralf]

Hi Wayne and thanks for your thoughts and comments.

My situation is that I want to have the database in a Catepillar that weights metal blocks. The Cat picks up these blocks in another part of the production hall where we don't have any network coverage. The blocks is then driven to the weight scale for measuring. Here we will have network coverage and it is here we will communicate with the weight terminal (wireless RS232). The weight data is intended to be put into the database from a form. The weight value will be accessible through an activeX control. So when the operator presses 'Enter' on the laptop, the current record is filled with the weight value.
When the operator drives away to the storage area, there are again no network coverage. The weigh process only takes a couple of minutes, the time the Cat has network coverage. The time outside network coverage may vary from a couple of minutes to several hours.

Unless the operator closes down the db when he or she drives away, I guess the database will stop working - with the risk of corrupting the db. Shutting down the db is no option though, because this will be to innefficient or the operater just forgets to do so.

I haven't built this yet, but I'm planning to do so. I'm just doing some reasearch around this because it is quite expensive only to by the hardware for this project.

If anyone have any good ideas or knowledge abot this, I'll be most gratefuk for any help or advice.

Thanks in advance

 

[Crilen007]

Hmm... I would first check the connectivity in the area. if there is lots of interferance I would not go for it.

Buy/borrow a wireless setup and see how well they communicate across the area.

Run some network tests... thats the only way to tell.

Wireless has diminishing quality in signal, but that usually just slows it down.

I would verify the signal integrity before I did anything else.

 

[geralf]

Hi Crilen007

Thanks for your input. In Norway we are only allowed to use 100mW of output power on a WLAN access point. (1w in US I think). This limits the coverage area to to about 400 to 500 meters. I'll see if we can arrange some tests. Instead of using the main database, I wondered if I can make a very simple database, split it and place the BE on the server. If I link from the main database to the 'Weight database', do I I then face the risk of corrupting the main db?

I'm also playing with the thought of running only a local db on the laptop (only wireless communication with the weight scale), and on a regular basis synchronise with the main database.

Any ideas/thoughts will be appreciated.


TIA