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Check if file reference available


Genx
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Is there anyway to check if a file reference is available? The reason i ask is that my solution is hosted on a wireless network that might crash once every couple of hours. Point is, the front end stays on-line and the back-end crashes. I want to be able to "re-connect" to the back-end file reference or at least re-open the front end which does the re-connecting for me, on the condition that the file thats referenced isn't available.

Cheers,

~Genx

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I'd put some serious effort in making the network stable. FMP to FMS relies on a persistent connection and if it gets cut off in the middle of a data transfer then you may get corruption in your file or at the very least inconsistent data (half records, incomplete fields,...).

If not then what you'll need is a full transactional model with loads of error checking and handling. Have a look at the errors that FM can return (it's in the help file) and decide which ones you need to catch in your setup and how to handle them.

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Ok, well i have a log out button currently available throughout my solution i might just tack on a custom dialog giving the option to 're-connect' or logout.. i can't really be bothered with that much error checking at this point, the file is far to large and the unstable wireless network can't be helped, though crashes are minimal at about 1 every 2-3 hours and data entry is not constant.

Question is though, is there any way to refresh the file reference without re-opening the file?

Cheers for the input Wim,

~Genx

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though crashes are minimal at about 1 every 2-3 hours and data entry is not constant.

YIKES!! I call a crash once very 2-3 years minimal.

Genx. Like Wim said I would give some serious thought to this instability cos it only takes the one instance where someone is entering or manipulating data during a crash and you might find you have a much more serious concern than whether you can refresh a file reference.

Trust me - I have been there - It is not a nice place

At very least make sure that you have virgin (uncrashed) backup of the solution available.

Phil

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I think people are misunderstanding my problem. The server isnt crashing... the wireless connection is simply disconnecting causing the front end to lose the file reference. The backend file itself remains open and hosted on the server. FM Server is unaffected... My problem is simply that if the file reference is lost, the opener file must be located on the desktop or wherever and opened again (I disallow recent files). The persons current layout is lost, they have to login and do everything again.

My current thoughts are that i simply automate the login (i store the login and password in a global field which gets stored as a global variable post log-in) and take the user back to their current layout. Instead of opening the opener file, going to the login screen and having to navigate there...

SERVER IS NOT CRASHING, its the wireless connection. Just thought id make that point clear here..

Anyway, if there was perhaps someway to refresh a file reference, i.e. get FM to search for it again, than these scripts wouldnt be necessary..

Cheers,

~Genx

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Ahh, but the problem is that network interruptions CAN cause the hosted file to be come corrupted and even trashed... especially if you are modifying database structure at the time (define relationships, fields etc).

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Ok, to cut it short, the file isn't being modified, layouts arent being viewed, only data is being exchanged requested and exchanged. And this only happens when someone browses, finds, commits etc. It isn't constant... except that a record may be open. But there isnt that much other interaction with it... And i can't help wireless disruption in the surrounding area and i'm not the network admin anyway so it's not up to me, and we're bridged across a 100m gap so that doesnt help much either, its now two wireless connections. Point is, it can't be helped, and i'm not sure there'd be any critcal file corruption though i called fm tech support about something similar the other day, i may ring them again to double check. Now finally anyone know of a way to force filemaker to refresh file references without opening the whole file again?

Cheers,

~Genx

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Surely the FM engineers wouldn't have been so stupid as to not account for network crashes, wireless or otherwise... i mean what if the power wen't out and though the ups kept the server on, the router or ethernet switch died, or what if there was a fault in some of the cabling, or what if a WAN died... FM claims to work for 250+ users at once, how often do you think network problems would come about then, a file couldn't be swapped every time someones laptop died while connected to the server etc.

~Genx

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Sheesh... somebody like Wim advises to get the network stable, and you're arguing?

If somebody's machine was running a process that got interrupted part way through, it wouldn't necessarily corrupt the files or cause FMS to crash, but it could leave the database in a state that is no longer consistent with the business rules. The result is the same though: the data is corrupted.

The bigger the files, the more users there are, the more chance there is of this happening. Which is why getting stable network (and power) is critical.

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Sigh, i'm not arguing, i thought i was being mis-understood, how on earth do you stabilize a wireless network. Changing the angle of the computer, or a tiny bit of radio interferance can cut of a connection immediatley... And if filemaker is so sensitive to computers to disconnecting, its should say on the box: "not suitable for wireless networks" ... However, i thank every one for their suggestions though i don't think my original question was answered some other important issues have been raised. Thanks to everyone for the input, sorry if it seemed like i was arguing, i just thought i was being misunderstood (see above).

Cheers,

~Genx

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I talked to tech support, they seem to agree, that there is only a small chance of corruption, and even that will only occur in the case that data is being transmitted to server during the connection break.

However, a textual transmission will take very few packets and sends almost immediatley, so on a 54mbps connection, there is little chance that a break will occur during transmission. Furthermore, even if it does, the chance of corruption is remote.

I do however do routine weekly backup's, not of the file itself but rather of all the data in .txt form both locally and remotley so that in the case that server file corruption does occur, the data is restored into a clean "virgin" file.

My question is now changing a bit, in terms of my backups, i manaully execute the script, though the script does all exporting, zipping, uploading etc. itself, i still have to manually execute it. Is there anyway to trigger a script at a certain time of day on a server that doesn't have FM Pro installed...

Cheers lots for the advice so far (and the heads up on the whole issue),

~Genx

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Warnings on the box are no substitute for understanding how FMP/FMS works and how networks function. FMS can work well on wireless network. Just not on crappy ones. And not on crappy wired networks either. And not on decent networks with crappy hardware.

Crashes will happen and that's why you need a good backup & restore strategy.

And a strategy for dealing with incomplete data in your records. If transactions are important to the business (inventory, invoicing/accounting,...) then you need to write code so that you know whether a transaction succeeded or failed.

Check out one of the recent FileMaker podcasts featuring Todd Geist for more info on this.

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Cheers Wim,

Though in this case transactions aren't critical, it would be great to know how to check if a transaction succeeded or not. So i'll take a look / have a listen at the podcast.

Thanks again everyone,

~Genx

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"My question is now changing a bit, in terms of my backups, i manaully execute the script, though the script does all exporting, zipping, uploading etc. itself, i still have to manually execute it. Is there anyway to trigger a script at a certain time of day on a server that doesn't have FM Pro installed..."

So the file isn't hosted in FileMaker Server? Is it hosted with FMP or does it live on a shared network volume?

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It is on FM server, i just have no clue how to schedule script execution...without actually opening a filemaker file... in filemaker vs. filemaker server.

Edited by Guest
clarification
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Wim, just as a side point, the hardware and the network itself have both been Cisco certified... To clarify one last time for the sake of it, what i mean is that each client is likely to disconnect sometime in a 3 hour period... its just an estimate Not all at the same time, just randomly...

I.e. yesterday, only one of my clients disconnected, out of 15 people, sometimes its worse (more in the range of a disconnection once every 3 hours), sometimes its even better, but it doesnt change the fact that disconnections do happen no matter how good your hardware or your network.

~Genx

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"... disconnections do happen no matter how good your hardware or your network"

Sure. It's just that your idea of "normal" is off by several orders of magnitude.

I run a FMS 5.5 network that is hosted in Sydney and has users in Sydney and Melbourne. All connect through FMP client. Average number of concurrent users is around 15. Disconnections are so rare that when they happen I get phoned personally! That happens about twice a year.

I think you're seriously underestimating the stability of an optimised FMS/FMP setup. It can be set up so it "just works" for years and years with nothing more than frequent backups and regular server restarts.

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Are you telling me that none of your users will ever drop out of a wireless connection? Or if they do it will happen two times a year?

You're telling me they never, shut their laptop while the solution is running? Never have any disturbance interfering with their wireless?

If so, please please tell me the hardware your using and i will make sure to recommend such great hardware to all my users from this point on.

Honestly if you've got a wireless connection that might disconnect on average one of your 15 users two times a year i'd LOVE to know about it.

(Just out of curiosity though, if they're network connection winked out, wouldn't they go to their network admin, why do you field these calls?)

Cheers in advance,

~Genx

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  • 2 weeks later...

Stablizing your wireless network connections:

I will assume that you have a single access point for your users at this time for the area you are supporting. The more interferance there is or the farther away your clients are the more likely you are going to get disconnects.

There are 3 solutions to your problem that you can attempt:

1) Use a wireless access point that supports the use of an external antenna. Purchase an external antenna/amplifier and connect it. This will increase signal strength between your clients and your wireless access point and decrease the likelyhood of your clients disconnecting.

2) Drop a new wired connection closer to your clients that are farther away from you primary wireless access point and install a new wireless access point there. They can then use this to connect to the network instead of the access point that is farther away.

3) If option 2 is not doable because you cannot pull a drop that close to your clients or the drop would be too cost prohibitive, you could setup 2 wireless bridges and then install a new wireless access point closer to your clients to accomplish the same thing.

LEGEND

WN = wired network

WAP = wireless access point

WB = wireless bridge

/// = wireless connection

--- = wired connection (10BaseT/100BaseT)

WCW = Wireless Client Workstation

Example 1:

Addition of a antenna/amplifier to your access point

BEFORE

WN --- WAP //// WCW

AFTER

WN --- WAP >> ANTENNA //////////// WCW

Example 2:

In addition to your existing wap that your clients used to connect to, you now have a new network drop closer to your client workstations with a new wap for them to connect to which will increase signal strength

before

WN -- WAP ///// / / / / / WCW

after

WN -- WAP ///// WCW (closer clients)

WN --------------- WAP //// WCW (farther clients)

Example 3:

use of existing wired network, 2 new wireless bridges, 1 new wireless access point to place a new wap closer to your client workstations without having to install a new wired network drop

WN --- WB ///////// WB---WAP /// WCW

It is important to note that if you choose to use wireless bridges, the type of bridges you purchase depend greatly on the enviornment they are being installed into.

Wireless bridges which use directional antennas have longer range but generally require line of sight. Wireless bridges that do not have directional antennas are a bit more adaptable, but have a shorter range and are prone to the same signal interferance issues. They can however allow you to bridge weak points in your network, where you can then run a longer wired drop to your wap to bring your client workstations closer.

If you have no ability to create a stronger network connection, you will always have a remote possibility of data corruption. Which no matter how you look at it is a very bad thing.

Edited by Guest
Added additional info for bridges
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The way i actually have it set up is as follows: 2 sites, 400 m appart with a 2.4ghz wireless bridge connecting the two sites with a WAP on both sides. The WAP on either side isn't further than 15m from any user with little or no interference from any walls inbetween. I have used an amplifyer for home purposes, with fairly decent results so i might give that a go...

It might also be the client side network cards... I might trial some usb adaptors on a couple of them and see if the cards being external improves the performance at all..

Cheers for the suggestion,

~Genx

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Two sites, 400m apart... I hope you're using a directional antenna to focus and boost the signal going both ways between your bridges. I'm pretty sure 1200ft (at least) is pushing the limits of your wireless bridge.

You may also want to consider restricting access to your WAP stations to a single protocol. Either 802.11b or 802.11g. Not necessary, but I personally think it helps.

External cards typically have better reception than internal cards. I don't have much experience with USB wireless clients though.

I just thought of something you could try. Take your laptop and connect to one side of your network, and ping a machine on the other side. Let the ping run all day, and then check the stats to see how many dropped packets there were. A lot of dropped packets may indicate a disturbance in the Force between the two LANs. Plus, a single machine running a ping program all day long shouldn't burden your network too heavily, and if you should happen to notice the lost packets immediately, running it all day would probably be unnecessary.

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No, they're very directional, it was set up by cisco with telescopes : around a month ago and the performance has been great. As per the ping, how would i run it all day and report over perhaps only the dropped packets.

Help appreciated :,

Cheers,

~Genx

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Cool on the telescopes. :-)

As for running a ping, most Unix ping utilities will repeat a ping until it is told to stop. Once stopped the stats for the ping session are displayed.

I've never tried pinging from the command line interface in Windows, but I imagine it must do the same.

Be aware these are for very basic stats. If you want more detailed stats, hunt around the web for a network diagnosis program. There are a ton of them available for Windows, and some of them should be freeware or shareware.

Regards,

Roy

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Hmmm, yeah good thinking i will do that... but just so you know cmd will only try to ping four times in windows and return the results based on that.

Cheers for the suggestion though, i think i'll try it...

~Genx

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