Labview 6.1 takes 10 minutes to open 600 tags.

[Chris Grove]

We have created a LabView 6.1 application to read tags in a Modbus OPC server.
If we monitor 100 tags, the start-up is instantaneous.
If we monitor 300 tags, it starts in a few seconds.
Monitoring 608 tags takes 10 minutes to start.

How can we get LabView to start faster?

Server w/2 Xeon 1Ghz processors.
1G RAM.
This is the only process running on the server, save the ancillary stuff.

[Process_Systems]

This sounds suspiciously like the problem I had with 6.1 and Datasocket. There is a limit of 570 tags with Datasocket and 6.1. After this, the Labview built-in web server chokes, and errors out. After several calls to Austin, I found out that I had to update to 7.0 to overcome this limit. I would not be one bit suprised if you have run into a variation of the same limit. I can not be sure, of course, but the similarity is there.

Good luck.
Dave

[preston_johnson]

Have you considered the datalogging and supervisory control module for LabVIEW. This module has a very effecient Modbus server, and works with 1000's of tags very quickly. It is built for HMI/SCADA applications.

The module also has a built in alarming engine, historical database, security systems, graphics for the HMI, and so on.

Preston

[Alan Kilty]

I built the program from the LabView example "Multiple OPC Items Momitor". It uses the ICONICS Modbus Ethernet OPC Server 3.05 for communicating. The doc. in the example stated it used the dataSocket VIs that shipped with versions of Labview prior to version 6i as the dataSocket primitives shipped with LV 6i were not fully compatible with OPC. It reads the tags fine, after it opens them. The "OPENing" of the Tags is what takes so much time at startup. Currently I reading the tags one at a time in a "FOR Loop" which takes about 1MS per tag. I have been looking for a way to read a group of tags for one PLC, but the ICONICS OPC Server does not support this. Are there examples in datalogging and supervisory control module for reads OPC tags? Do they support
reading a Group of tags?

[preston_johnson]

If you chose to try LabVIEW Datalogging and Supervisory Control (DSC Module), I would use the National Instruments Modbus Driver. With LabVIEW DSC, the Modbus driver continiously polls the modbus items you are interested in at the rate you specify. These values are held in the DSC real-time database, and optionally stored in the DSC historian. DSC VIs allow you to read multiple tags at a time based on the group that you assign to the individual tags, or as specified by a tag list. I have attached a bitmap of the on-line help for the VI.

I'll be happy to help with other questions.

Preston Johnson

[Alan Kilty]

Thanks for the reply. I see from the on-line help you sent that the default scan time is 1 second. How well would it work using NI Modbus Driver scaning 600+ Tags every 250MS? The server I running on has 2, 1Ghz processors. Would it handle 6000 tags every 250MS using the above?

[ronil]

I have the same slow start problem even with the DSC module. After the Tag engine launched, I have to wait that certain time then I can perform the tag read.vi and tag write .vi. After this certain time passed the data read/write speed is very good. The wait time for 1600 tags is about 1 hour. Preston, do you have the slow start problem in your application? Thank you.