Is Shared Variable Engine with LV8 an OPC server ?

Hello
Is the shared variable engine with LV8 an OPC server ?
Does any OPC client can acces to Variable Engine OPC server an read shared variable ?
Can I build an installer and deploy my application with Variable Engine OPC server on other PC without LV8.
Thank you

Hi
You can communicate between an OPC serveur and LV8 and use shared variable. To deploy an LV8 exe application, you must have the run time engine installed on the PC without installing LV8. You can create a setup with LV 8 in which you can integrate the run time engine.
Kamal
NIF

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Shared variable engine with pro-face touchscreen windows 2000 professional

hello,
who has some experience with the shared variable engine from LabView 8.5 and a touchpanel from Pro-Face?
We try to deploy shared variables from the touchpanel but it doesn't work. Additionally the windows service ni shared variable engine dosn't start and we can't start it manually .
The touchpanel is a PS3701A from Pro-Face with Windows professional 2000 for embedded, Pro-Face told us that we have the full service of Windows 2000 professional on a regular PC.
Many thanks in advance
derN

Hi Andrew,
Thanks for the feedback! Your feedback will help us to improve LabVIEW for our customers. This bug has been reported to R&D (#45493) and they are currently investigating this issue. For now, the best workaround appears to be using a different OS, as this seems to only occur in Windows 2000. Thanks for the feedback!

Shared variable engine OPC delay

Hello All,
I've got a bit of a problem with the delay time of updates between a non NI OPC server and a shared variable engine OPC client. I am using the redion OPC software OPCWorx with a database of around 120 tags to monitor and log data from a small pilot plant. The OPCWorx server has been configured with a 500ms update rate and the NI OPC client as the same. So here is my problem; logged updates occur no faster that 2.5s which is fine as we are exporting in 3 sec intervals (would still like to increase the performance of this to around 1 sec) but the main nuisance is the delay in changing control registers in the PLCs. The controls and indicators are directly bound to the shared variable items where by a change in a boolean control on the front panel to the indicated response can range from 5 to sometimes 15 seconds delay. If I bind the same control and indicator directly to the OPC item through the data socket the delay in response is almost unnoticeable at around 1 sec. I have increased the update/logging dead bands of the shared variables which seemed to help but only by a second or so.
Im wondering what the limitations of using an OPC shared variable engine is and if this is expected or have I gone wrong somewhere. All the variables are configured as non buffered and to have single writers.
A few changes have been suggested;
- Upgrading the PC. The current hardware is AMD Phenom 2 3.21GHz processor, 4GB of ram running windows XP.
- Using Modbus over ethernet instead of OPC.
This is the first major use of the DSC module and using the shared variable engine as an OPC client so any information or insight to help with this would be much appreciated.

Hi Kallen,
The Shared Variable Engine can become bogged down when there are more than 100 shared variables. This may be what you are experiencing. We can check buffering for the variables and disable it, and that should improve performance slightly. As it is, using datasockets may be the best method for over 100 shared variables. I apologize for the inconvenience.
Here are some KnowledgeBase articles that can be of use with regards to this issue:
How Does Buffering Work for Shared Variables?
http://digital.ni.com/public.nsf/allkb/5A2EB0E0BC56219C8625730C00232C09?OpenDocument
Why Is Accessing IO Variables Through The Shared Variable Interface So Slow?
http://digital.ni.com/public.nsf/allkb/F18AEE4BE7C9496B86257614000C43DF?OpenDocument
Matt S.
Industrial Communications Product Support Engineer
National Instruments

Error with the Shared Variable Engine

Hi,
I have a problem with the Shared Variable Engine,
A .doc File is attached to this message, decribing the problem with pictures.
I will be glad if anyone can help me.
Sincerely yours
Amitai Abramson
Attachments:
Question.doc ‏819 KB

Hi Amitai,
Good afternoon and I hope your well.
A member of the team from NI Israel contacted me regarding this post.
I want to provide you with extra details on how to resolve your issue - i.e. Repair (Or Re-install) the Shared Variable Engine.
If you use the MsiBlast Tool it will populate a list of all MSI NI Installers. One of these will be NI Variable Engine. On the right-hand side you can the click 'Repair'. I would also Repair the engine support for the versions of LabVIEW you have installed. Please see attachments for MsiBlast and a screenshoot of the MSIBlast screen.
If this doesn't work I would recommend re-installing LabVIEW using the following guide, which I posted on this forum. (second post by me).
Please let me know how you get on,
Kind Regards,
James.
Message Edited by Hillman on 12-03-2008 12:19 PM
Message Edited by Hillman on 12-03-2008 12:19 PM
Kind Regards
James Hillman
Applications Engineer 2008 to 2009 National Instruments UK & Ireland
Loughborough University UK - 2006 to 2011
Remember Kudos those who help!
Attachments:
Repair Shared Variable Engine.JPG ‏97 KB
msiBlast.zip ‏110 KB

Appear to lose connection with the Shared Variable Engine

Have been through the boards, but with no success regarding the specifics of my problem.
I am running a real-time application on a PXI-8108. The host software is taking care of user interface, etc. Information exchange is handled using Unbound Network Shared Variables (located on the host, though problems occur no matter where the variables are located). Everything deploys fine. Software runs swimmingly. I have backed off the DAQ/communication processes until the RT cores are at <10% busy. However, occassionally while running, I get a popup "Waiting for Real-Time Target xxx to respond..." If this message stays up for long enough, then the target's attempts to read the Shared Variables start erroring out with an error -1950679035. As the variables have already been deployed and used prior to this instant, I find this curious. If I filter out the error, eventually the real-time software comes back up and everything progresses as though nothing happened. However, this is a potential deal-breaker for the users who can be impatient with having to wait a few seconds for the software to respond.
Any idea what is happening? I'm not pumping huge amounts of data over the network, no threads should be starving. Kinda confused.
Dan M.

The shared variables are being used much like how a queue would, directing each loop to perform an action should the host require it. If no action is required, then the loops default to check their respective bus or DAQ.
Currently, I am running 13 timed loops (whose periods I have extended signficantly during debug to no detrimental effect of my software, but to no improvement in the issue in question):
RS-232/J1708 converter loop (50ms period)
CAN loop (50ms)
DMM loop (250ms)
Oscilloscope loop (250ms)
DAQ loop (50ms, includes 1 AI task, 4 DI tasks, and 6 CTR in tasks)
Switch loop (50ms)
RS-232 loops (50ms for the main, 1 additional loop at 1Hz)
RS-485 loops (50ms for the main, 4 additional loops at 1Hz)
Both cores appear to share the load, usually the aggregate load is under 15%. When the popup appears telling me that the host is waiting for a reply from the target, the PXI controller monitor output still updates the CPU loads, which do not show anything unusual, such as a spike or a freeze in loading. The target loading does spike up to about 30% total after the communication is reestablished, but that appears to be the software attempting to "catch up" with the events that occurred during the "black out".
The error reads like this:
Shared Variable in Main Target Application.vi
This error or warning occurred while reading the following Shared Variable:
\\My Computer\Host-Target Interface\RS-485 Messages to Target [<--insert other variables here]
\\192.168.1.122\Host-Target Interface\RS-485 Messages to Target
Unable to locate variable in the Shared Variable Engine. Deployment of this variable may have failed.
Are there any other drivers that would be starving the Shared Variable Engine? For example, if a VISA or NI-DAQmx driver goes to sleep, could it hold up the SVE? What execution system are they running under?
Thanks for your help!
Dan M.

Shared Variable Engine OPC Server & Matrikon OPC Explorer

Hello All
I have a shared variable Engine OPC server running on my IPC. I am querying NI OPC Server through Matrikon OPC Client. My situation is if shared variable engine process is switched forcefully off (NI DSM) or communication between server and client is lost then client is crashing which is quite obvious. But the problem is if Server is Up again then the client is not connecting to server automatically.
First of all is it possible, that if server is up again then it will try to send some signals to the priviously connected clients ? If yes then do i have to make changes in shared variable engine properties ? How i can do this ?
I hope you all will understand my problem, if not please post you doubts. I will try to clear my points.
Thanks & Regrad´s
Varun Garg

Hi, just now I face a similar problem. When clients restart connection, the variable engine crash, for now the only way founded is restart the program programmatically, but I'm interested in how fix that.

Shared Variable Engine Error Handling

I have a HMI system that connects through shared variables to an OPC Server. I have encountered problems with Variable Engine, and a problem with tagger which I don't know anything about. I checked OPC Server to see ifit's installed properly and the items status is good, and the server's connected. I tried to restart the shared variable engine service but it doesn't reply. When I monitor variables there's no connection. I used Alarm&Event query.vi in my application and then encountering tagger error, server connection failed. How could I handle these errors?
I appreciate any help.

I've created Bindings to OPC items I want to read/write through an OPC Client instance, bound front panel objects to these shared variables, deployed the entire library and run the VI.
All the connections were true (green PSP-LED. through the Monitor Variables all the variables and OPC items of client instance had good quality and right value.
All the variables were configured to log data and alarms.
Configuring the library for a data base through it's DSCsettings:database, I used Historical VIs (Read trace,… ) to retrieve data from citadel and they worked properly. I used Alarm & Event Query.vi to retrieve alarms from citadel, the VI encountered this Error:
        "Some part of tagger encountered a problem and should be closed"
After that the entire connections failed (PSP-LEDs goes red) and the I/O Engine couldn't be restarted and shows this Error:
             "Could not stop the National Instruments Variable Engine Service on local computer.
              Error 1053: the service did not respond to the start or control request in a timely fashion."
And the variable monitor dosen't show any library and variables.

What causes the Shared Variable Engine to Crash?

All,
Some background info:
I am using the SVE and DSC so that I can log my data to Citadel using Data Sets. I converted a previous DSC 7.1 project that used the tag engine over. That app ran for over 18 months. Need to upgrade app and add features at my customer requests so we migrated to LV 8.0.1.
I have an app that crashes the Shared Variable Engine (SVE). I created a test app with a single SV and then created a control and bound it to the SV and it works every time until I launch the larger app. The main app only has 33 SV that are set when I receive TCP data from PXI RT system (not using SV on RT since the logged data is only a fraction of the total data streamed and I don't want to take apart the RT data and send the SV separately). I have bound front panels controls to the SV's. When I run, I get server connection has been closed. I verified that the SVE was running with the test app before launching the main app.
I deploy the shared variables in the application and have verified they are deployed by the Monitor Variables utility ... but it always shows "No Value" for the data fields. I have set logging to enabled for data only, set Value Deaband (%) to 0 and Value resolution to 0, Update Deadband is Disabled as is Alarming, Scaling, Initial Value and Description. Security is set to default. All of the variables are set to Double, Network-Published, Single Writer with Buffering and Bind to Source disabled.
I have verified that the SV deploy without error by clicking Deploy from the project. Autodeploy All is off but I get the same results with it On (checked).
I undeploy and kill the process when I close the application.
I have tried only using 1 or 2 of the SV in the main app but get the same results. Every once in a blue moon it will work after rebooting the PC (but not everytime). Once it dies I have tried running NI examples as well as the test app and they fail until I reboot.
The error code indicates that the SVE engine has crashed. I have changed the service settings on Windows to relaunch on 1st, 2nd and all times after but nothing restarts the SVE. After it crashes it is impossible to exit LabVIEW without it hanging or reboot the PC without pressing the hard On/Off switch.
Once it dies there is nothing that I can do to get it back alive without rebooting the PC (a real problem for a control and monitoring system).
Any ideas would be greatly appreciated
Thanks.
Randy

Randy
Sorry for the delay, I've been researching your issue and juggling a few other issues. :-) One thing we can check is the Windows Event Log which will give us some more details as to WHY the Shared Variable engine seems to be blowing up on us (Conttrol Panel -> Administrative Tools -> Event Viewer). Any details in there along the lines of Variable Engine or Tagger crashing will help us narrow down what's going on.
There's always a possibility of files not getting upgraded correctly; however there aren't many shared components between LV 7.1 and LV 8.0. The Shared Variable engine is entirely new and the installations of LabVIEW themselves don't share many files outside of the example finder and a few other small common components (things located in the appropriately named Shared folder) I keep both on my machine (in addition to 5.1, 6.1, 7.0, and 8.2) without any hiccups.
The SVE crashing I have seen in the past (and from internal bug reports) has been from buggered installs, so uninstalling and reinstalling DSC may be a good course of action. One good test to do in the middle is to see if the engine still crashes with DSC uninstalled.
Hope this helps.
--Paul Mandeltort
Automotive and Industrial Communications Product Marketing

How do I install Shared Variable Engine on a computer not having Labview?

Hi,
I am trying to communicate with a real time program running on Compact RIO through shared variables. I have an executable of the host vi that runs on a Windows computer. If I run this executable on the computer that has Labview installed on it, it functions fine. I want to be able to run this executable on a computer with Labview. I learned that I have to first install Shared Variable Engine on this computer.
How do I do that? Where to install it from? Is that going to be sufficient? Please provide the solution or point me to the right resources.
Thank you.
Anmol.

When you built the installer for the executable, you have a choice to include additional installers. One of them is the "NI Variable Engine". Have you tried including it?
LabVIEW Champion . Do more with less code and in less time .

RT cRIO: Shared Variable Engine Errors

This is an app written in LV2011 running on a cRIO-9076 (Scan mode), with the August release of software installed on it.
I have gown to great lengths to try an optomize my code, I have reached an impasse. The VERY FIRST TIME I run the code on the target (be it via a self-starting EXE or targeting from my Windows development machine I am able to read and write to several shared variables, but then when I access them again (possibly when I am starting a couple timed loops and the processor is very high) I get this:
Error -1950679023 occurred at Shared Variable in targetIdleLoop.vi->ZDAQ_cRIO_Target_Main.vi
Possible reason(s):
LabVIEW: (Hex 0x8BBB0011) The connection to the server was disconnected.
This error or warning occurred while writing the following Shared Variable:\\ZeeAero-RIO1\variables - network - RT (separate)\RTStatus\\10.10.10.10\variables - network - RT (separate)\RTStatus
If I go back to the Dev machine and restart the code, I don't get this error; it only happens after a reboot.
BUT on this second run (or subsequent VI starts), when we get to that same point, a client priogram running on Windows and reading a network variable successfully suddenly gets:
LabVIEW: -1950679035 (Hex 0x8BBB0005) Unable to locate variable in the Shared Variable Engine. Deployment of this variable may have failed.
Which lasts a minute or so, then goes away. The code is made to loop, and when it loops back through this point there are no errors at all.
So, to recap:
1st Run after reeboot, 1st loop :Error on Target (0x8BBB0011), connection to server disconnected
Subsequent Runs, 1st loop: Error on Windows Client (0x8BBB0005) Unable to locate variable in the Shared Variable Engine. Deployment of this variable may have failed.
Subsequent Runs, 2nd+ loop: No error
Here is a link to a screenshot of the installed SW on the Target:
EDIT: I should mention that there are three loops running in parallel on this app; 1 is a Timed-loop (at the moment) set to a period of 10ms with 100 priority, #2 is also a timed loop and is set to 3ms with priority = 50 and the third is a WHILE loop with a 50ms wait. The error occurs during the WHILE init phase, which happens once per run, not repeatedly.
Solved!
Go to Solution.

This is killing me. It's obviously something to do with when the Timed loops start AND when I access the network variables.
See the screenshot below.
Note that I read and write to several network variables in Subroutines to the left of this screenshot at startup. The starting of the timed loops causes the issue with the shared variables. (also note that the periods are set to 100ms and 99ms in my testing after the initial 1st loop.
Now look at the Wait at the bottom set to 10 seconds. In this case, it will work. There is no error at breakpoint 37 if I wait around 10s. If I DON'T wait the 10 seconds, there is an error after the check on the BOOL "stop - Network" variable that NEVER GOES AWAY. If I look at the CPU monitor, there is an initial bump in the cpu when starting the loops, and then it drops to about 15%. But if I don't have that 10s wait, there is ERR 0x8BBB0011 and the CPU spikes to 75% every 5 seconds and it never goes away.
And that's only the 1st loop after reboot. The 10s makes this work, but I still have an issue with it once I start doing individual runs (loops).

NI Visa - Shared Variable Engine

Hi,
I am using labview Shared Variable Engine to create variables on my workstation and bind them to variables on my server.
I have labview 8.2 installed on my workstation and labview 8.5 installed on my server.
The communication between them worked perfectly and I was able to use the variables created in the workstation.
In my application I need yo use NI visa to take serial input. So I installed the NI Visa on my workstation and the NI visa worked.
However, the Server was not able to see the variables I have created in my workstation.
Does this mean that NI visa do not work in parallel with the Shared Variable Engine, or does the NI visa change some of the settings parameters that would stop the Shared Variable Engine from working properly.
Thanks in Advance

This information helps me get a better idea of what you are doing, but I need much more information in order to help pinpoint what is happening in your application. You should absolutely be able to use VISA as well as the Shared Variables concurrently. What is the device that you are using for data acquisition? I'll need the model of the device. What kind of data are you acquiring? How are you using VISA to communicate with your instrument?
One other item is to look in the distributed system manager to see if your shared variables are actually getting updated
Any code you could post here would help as well.
National Instruments
Applications Engineer

Deploy Shared Variable Engine in localhost

I need to talk to multiple RTs using single computer. It seems
obvious to deploy shared variable engine (libraries) in localhost instead of
RT. However, the problem is the shared variables (read) used in localhost VIs
are not being updated from RTs. But when I am using another local VI to update
the shared variable, it is working just fine. The variable path of the RT looks
like "\\My Computer\Local NPSVlvlib\Test
Data". I think this is the problem why the values are not being updated
because RT cannot resolve the network path ("\\My
Computer\Local NPSVlvlib\Test Data"). Also, I tried to change the shared
variable path in RT but I could not do it. Help Needed!!!!
Solved!
Go to Solution.

Thanks for your reply. I found in this link http://zone.ni.com/devzone/cda/tut/p/id/9900#toc2 that host computer can host the shared variable library and RT does not need the shared variable engine. See below
If your application includes a single host computer and a single or multiple RT targets it is recommended to host the library on the host computer. This will save memory and processor time on the RT targets. Also, by hosting the library on the host computer instead of the RT target, you can reduce the software install footprint on the RT target. The RT target will not need the Network Variable Engine, but will still require Variable Client Support. The Network Variable Engine allows hosting, the Client allows communicating with libraries on other machines. You can see a RIO target with these installed in Figure 4.
That exactly what I am trying to do. Any comments?

RT Shared Variable Engine stops publishing

I have an RT system (PXI-8106) that hosts quite a few network published shared variables (NPSVs) for communicating to a Host PC. My Host and RT executables have been functioning fine on their respective systems for weeks, but just recently, I started running into problems with my NPSVs. My Host application has indicators to display DAQ data being acquired on the RT target and transferred via NPSV, and lately the application will update normally fine for several hours and then the displays will stop updating all of a sudden. If I reboot the RT target, the communication is restored...for a couple hours, anway, until we get another NPSV lockup. I can see no rhyme or reason as to why it stops updating the variables when it does; it seems to just randomly crap out.
It just happened again, so I brought my development laptop down to run the Distributed System Manager. Sure enough, the NPSVs all stopped updating (latest timestamp was about 30 min previous to my check). I know, however, that the RT system is still running (I can open remote front panels), and none of the NPSV calls use their error input clusters, so an upstream error would not be causing the issue. Also of note, I have a couple NPSVs that are aliased to PSP URLs (NI_SystemState\CPULoad), which do continue to update while the remaining NPSVs do not. So that seems to indicate to me that it is not a networking issue, nor is it a Shared Variable Engine issue.
I also programmatically deploy the NPSV library from the Host to the RT target on initialization, so I know they are deployed properly. Redeploying does not kickstart the RT SVE into updating. The only thing that seems to solve the problem (albeit temporarily) is a reboot of the RT target.
Does anyone have any ideas as to what might be causing the RT to stop updating the NPSVs? I have already check the NPSV Troubleshooting KB (http://digital.ni.com/public.nsf/websearch/6E37AC5435E44F9F862570D2005FEF25?OpenDocument), and none of those suggestions appear applicable in this case (most address networking issues that result in never being able to read the NPSVs in the first place, whereas my problem is NPSV communication dropping out arbitrarily). Has anyone else run into such a problem?
Thanks!

I think I have an idea as to why my NPSV communication was freezing. One of my NPSVs is a 2D String Array of Alarm History Data, which just published infomation about alarms that have been triggered on the RT system; each new alarm appends a 10 element string array onto the 2D string array. For the most recent testing we were running, there was a recurring alarm condition that was not applicable (i.e. did not need to be handled--it just kept adding new elements onto the history array), and I am guessing that the array may have just gotten too big. When the RT target kept updating the NPSV (at 1 Hz) with more and more 2D String Data, it may have caused a buffer overflow for the shared variable.
I will attempt to recreate the problem on another system to verify the cause.

Deploying cRIO as Shared Variable Engine

I am finishing up a project where a crio will be continuously recording data and the computer is running a program that will download the data once daily as well as comunicate with the program running on crio device over shared variables. Since the crio will be using a cellular modem to connect to the internet, connection loss is expected. For this reason we have made the crio serve the shared variables so that if connection is lost to the PC, the crio will continue to record data normally without problems when it writes to or reads from the shared variables.
The crio will be running headless. I built a real-time application and deployed it as startup successfully on the crio device without warnings or errors. I connected to it via font panel to confirm it started up and is working properly. I will eventually use the application builder to build an installer that will install everything needed to run the program on the PC side. However, when I open the 'Belle Glade System PC' and run it, it attempts to deploy the shared variables on the crio device. It warns me that it will close any applications running on the crio device. This is not what I want. The shared variable engine is already deployed on the crio device and the program is running. All the PC program (Belle Glade System PC) needs to do is run and connect to the shared variable engine already deployed. I am obviously doing something really fundamentally wrong here and I could use some help.
[will work for kudos]

I apologize for not posting the solution to the problem.
Basically what you end up having to do is create two nearly identical shared variable libraries, one on the pc and one on the crio. The library on the PC has each of its shared variables binded to the corrosponding variable in the cRIO Shared Variable library by PSP URL (ip address and variable location). To do this, open the PC shared variable library and go to the properties of a specific variable. Check "Enable Aliasing" and under the bind to drop down menu select PSP URL. Then hit browse and find the variable on the crio. Do this for each of the variables on the pc.
This option does not seem to be 100% reliable as it has trouble detecting connection problems between host PC and crio device. This is because shared variables look for a connection to the shared variable engine. However, both the pc and the crio have their own shared variable engine running as a host so there is always a connection as far as it knows, lol. This solution worked ok for me since I could not find a more relable option.
There is a better explaination on this post: http://forums.ni.com/t5/LabVIEW/cRIO-Shared-Variables-amp-stand-alone-application/m-p/797139?query.i...
[will work for kudos]

Shared Variable Engine clock is consistently inconsistent

From the annals of the weird:
I noticed a while back that the DSM displays a different time than my system clock when I manually change a NSV value. I didn't think much of this, but then I noticed that it is not just wrong but inconsistently wrong. Here's the time difference, in seconds, between the system clock and the SVE timestamp for a dozen NSV value changes [the SVE clock always lags behind]:
35, 14, 1, 18, 29, 2, 21, 24, 14, 17, 29, 20
I checked these numbers in two different ways: (1) with the "Time stamp" event property node with NSV events using the DSC module and (2) manually changing values with the DSM and comparing to the displayed Windows time.
What's the deal? The timestamp is completely useless to me with a seemingly random offset from the system time; it's by far the best way to deal with this little bit of unfortunate SV event handling behavior. Filtering event timestamps against system time is fairly standard procedure and I can't see it being useful with this going on.
This should be trivial to reproduce--does anybody else see this? If so, is there an explaination--or better, a fix?
[I should note that I have seen this but I'm running Intel core 2 duo, not an AMD multicore. I'm using LV and DSC 2010 SP1]

You may have to set up the Time Synchronization Services on the computer with the DSM running.
In LabVIEW Help, look for Shared Variable Engine Page (Options Dialog Box)
In DSM Help, look for Shared Variable Engine Time Server Configuration Box
I don't know if both are necessary but I made all the computers on my system point at the same time server. The time server is configured as an Authoritative Time Server under Windows. It is in turn slaved to our DSN server which follows a Public NTP server.
JohnCS

Is Shared Variable Engine with LV8 an OPC server ?

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