LabVIEW updates values from OPC server too slowly

[MichaelKitz]

I am connecting to a local OPC server (selectron) via DataSocket connections and DS access VIs in LabVIEW 6i. This worked well for several month. But for a few weeks now update times have been varying and are extremely long in most cases. I do not exactly remember the changes I had made, but am sure that they were only one of the following:
-adding a control or indicator with publish and/or subscribe via datasocket connection
-changing bool input to 'wait for updated value' or 'timeout value' for DS access VIs

Furthermore I tried to undo all changes without success.
Has anybody encountered similar problems of different update behaviour of LabVIEW with changed use of datasocket connections?

[Jeremy Braden]

Do you think there might be other things on your network slowing things down? You might also consider using the datasocket VIs from vi.lib\platform\dataskt.llb ? This way you only open the connection to the server once rather than every time you write.

[MichaelKitz]

I am not using the OPC server via network, disconnecting from LAN had no effect. The manufacturer of the OPC server also told me that network functions would not have an effect on the server if network capabilities were not activated. I cannot judge if that is right or if the support guy understood my question.
Until recently the access to the datasocket via datasocket connections on front panel elements worked fine. You may understand that I do not like the idea of changing the means of datasocket access all over my application just to try if this is a solution. I believe there must be another possibility because it did not need a lot of changes to 'make the application slow'.
Regarding all the postings I read about this I think I will have to try it.
Thank you anyway.

[Jeremy Braden]

I agree with your suppostion about something little must have changed to make the application run slowly. It is just hard or anyone to guess what changed on your machine. It could be a driver update, a newly installed program, or a virus. You may never find the cause without a reinstall of your computer. My suggestion addresses the most common cause of slow OPC calls with datasocket. It will be a lot of work and it will improve performance whether or not you find the present cause for a slowdown. If you are worried about long term viability of your program, consider upgrading to 7 which has the datasocket open and close on the functions palette. NI keeps older VIs around for a really long time, so do not worry if you can't upgrade.