Two UAServers in one UAGateway

Questions regarding installing, running and configuring UaGateway.

Moderator: uagateway

Post Reply
Jr. Member
Jr. Member
Posts: 1
Joined: 25 Apr 2019, 07:55

Two UAServers in one UAGateway

Post by StefanBr91 »

Hello together,

I have a question in terms of redundancy using the UAGateway.

I have two systems. "System-A" and "System-B".
In System-A I have a redundant pair of computers (X1 and X2). In System-B I have also have a redundant pair of computers (Z1 and Z2).

On X1 and X2 there is an OPC UAServer installed. The OPC UAServers are synchronized with each other.
Now I would like to receive the OPC UAServer's data from System-A in my System-B. So I installed the UAGateway on my Z1 and Z2.
I would like to add the OPC UAServer of X1 zu the UAGateway installed on Z1 and also would like to add the OPC UAServer of X2 to that same UAGateway.
Now if I receive an Alarm in System-A, I can also receive that Alarm in System-B. If I acknowledge that Alarm now in System-B... what will happen in System-A?
Why am I asking? Because, I know there are two UAServers added to the local UAGateway. And if I send the acknowledge now to the OPC UAServers by using the UAGateway, what will the UAGateway do?
Is it sending the acknowledge request to both OPC UAServers added to the list of OPC UAServers? Or does it only send the request to the first added OPC UAServer?

Can you please explain, what happens in this scenario?

Kind regards

User avatar
Support Team
Hero Member
Hero Member
Posts: 2522
Joined: 18 Mar 2011, 15:09

Re: Two UAServers in one UAGateway

Post by Support Team »


the UaGateway has no knowledge about the "synchronized redundancy" of your server pairs. The UaGateway has two separate connections to two separate UA-Servers. The UaGateway transparently mapps all namespces of server X1 and all namespaces of server X2 into his own namespace array. For UA Clients connecting to the UAGateway there will be two separate entry folders in the address space, there will be two alarm root objects below the "Objects->Server" node in the address space. If system A fires an Alarm, will that alarm be send via X1 and X2?
1) if yes, the UaGateway will receive 2 alarms
2) if no, the UaGatewqay will receive the alarm via the related serverspacific/connectionsspecific Alarm-Object (e.g. X2).

If you ack the alarm in the UaGateway, it will send the ack (call the method) on exactly the selected AlarmObject that has fired the alarm. The UaGateway can distinguish between the X1-AlarmObject and X2-AlarmObject via the combination of "connection and namespace" information it has used to map the namespaces of the underlying 2 servers. NOTE: we assume that you ack the alarm via the UA Alarms&Events (e.g. UaExpert->Alarm View)
Best regards
Unified Automation Support Team

Post Reply