Graphic values not updating in a Xenta 911 network

Issue

Values in graphics from Xenta and Lon devices under a Xenta 911 network are not updated. Some values show database values and some values are showed with red crosses. When clicking on the value in the graphic the value is shown correct. 

Product Line

TAC Vista

Environment

TAC Vista 5.9 with a Xenta 911 as Lon network interface.

Cause

This could happen if many Lon and Xenta devices under the Xenta 911 is offline. When Vista do a online poll for a Xenta or Lon device and don't get a reply the communication will be halted for 3 seconds because of retransmission and time outs. This would not be a problem if a Loytec interface was used as it can handle more then one communication thread at the time but the Xenta 911 only use one communication thread.
In this case it is possible to see the correct value when clicking on it in the graphic as that is a user command with much higher priority than updating values in a graphic have.

Resolution

Try to minimize the number of offline devices which reside under a Xenta 911 network in the Vista database as these devices will slow down the communication on the Lon network.