Hello:
I started with OPC in Labview 6. The only two functions that I need is "read multiple tags" and "write tag". The tags are either located on the same PC or on a different one. I use Labview as an OPC client. The number of tags that i need to acquire is in the range of 2000-5000, once per minute. In Labview 6 and 7, all experts in the discussion forum and at NI said that above 100 tags, it was impossible to use Datasocket (performance issue when too many tags) and that the preferred path had to be DSC. So I started using DSC. Now that I migrated towards LabVIEW 8.20 the people at NI say that the best option is to use.... Datasockets! The read/write tags vi having disappeared the suggest me to make my own "read multiple tags.vi" and "write tag.vi" by encapsulating a "DS read/ write" in a for loop. As an entry to the loop, I would just wire the ref number that the connection ids that the Datasocket Open.vi supplies.
So my first question: why is this old Datasocket mechanism again the path to follow in Labview 8.20?
By curiosity I checked in Labview 8.20 what was embodied in the "read multiple tags.vi" that were shipped in the Labview DSC 7.1. And found that the very last layer of the Vi used... Datasocket read in a for loop.
So my second question: why was the Datasocket mechanism so poor in Labview 6 and 7 (for more than 100 tags) and now is the preferred way to go?
I cannot use the shared variable mechanism in my case because the entry of my application is a list of tags (2000-5000) to read and I just want an automated way to read these tags values in one take.
As I need to install the compiled application on dozens of PC I would prefer not to be forced to buy the DSC licenses on each runtime machine hence Datasocket that does not require the DSC license might be a good choice?
Thanks for all ideas and comments,
Christophe
