Bad Staus Codes

[bodo.david]

Dear Support Team,

We have UaGateway installed locally on a machine with an OPC-DA Server. For over a year everything worked fine, but now there are some new variables on the OPC-DA Server side we need to read. The problem is that when doing a normal one-time read on any of these variables, the Status code is BAD (0x80000000) and the value is null. But when creating a subscription, the Status is GOOD and the value as is expected. So the subscription is OK, but we need to read these variables as well.

Any assistance is appreciated, thank you.

[Support Team]

Hi,

the reason for that is mmost likely misbehaving DA Server. Already in the old DA Specification ad-hock read/write was allowed, and if compliant to the specification, the server should have delivered values when being asked "Read(from device)". Unfortunately there are DA Servers out there, that only deliver values if the tag is part of an active group and has already a value in the cache. However when first time added to the active group the Tag may have quality "bad waiting for initial data", and until than has no value and shows Bad status.

Reason of doing so different from the specification, is that "ad-hock" Read from device is extremly expensive call, compared to monitoring the tag on changing the value, hence some manufacturers decided to not support the ad-hock Read from device and allow the cache read only.

What is the DA Server manufacturer and version? Does it have a complicance certificate of OPC Foundation?

Please contact our support via website form and decribe the issue.