Slow OPC Server Connect L32E

[DRMoore]

Using 6.7.1 lookout, NI OPC server for CompactLogix 5300, (AB L32E), I have noticed that after 300 tags, After a cold computer boot, it will take about 10-15 minutes for Lookout to display data for up to 14 PLC's (L32E's), in real time.

Now that I am at 1,400 tags, read only, It will take about 45 minutes after a cold boot for Lookout to start reading all of the tags real time. I noticed a sharp increase in network traffic also after 45 min. With only a few write tags that I am using, I will enter a new value, the new entered value will display about 5-10 minutes later. If I wait for 45 minutes, then I get instant read and writes sometimes.

Any Thoughts?

[Alan_SCADA]

This could be the problem with automatic refresh requests that OPC Client is sending to OPC Server every 2.5 sec (IOPCAsyncIO2::Refresh2 call).

I started to experience this problem when I reach 500 tags. The automatic refresh request is causing a heavy load on communication because the OPC server must wait for all items in group to be physically scanned before it can reply. With the large number of tags this is becoming a problem within time window of 2.5 sec.

After some limit is reached server is starting to queue requests and that could be the cause that your system is starting to choke.

I am still waiting on National Instruments answer to my similar question.

Look for more at: http://forums.ni.com/t5/Lookout/Lookout-OPC-Client-Asynchronous-I-O-and-Update-Rate-serious/td-p/305...

[DRMoore]

This maybe a fix -

For the AB L32E PLC, the controller Properties menu, the Advanced tab, I changed the System Overhead Time Slice from 10% to 90%. The PLC scan rate will double by changing this.

Now with 739 tags using NI OPC server, from a computer reboot and  1 minute for the OPC server to see all 10 PLC's, I get instant read and write capability's on Lookout. Their was a 45 minutes delay before the PLC overhead time change.

Next test is to get the tag's up to about 1400.

[DRMoore · Accepted solution]

This fix did the job. 15 AB L32E's, 1025+ tags. Everythin is working fine.

"Open the property of the Device, and check the Protocol Mode on Logix Options tab. If it's "Logical Non-Blocking" or "Logical Blocking", change to "Symbolic" and see if it has better performance."