Opc Ua Performance Considerations - GE PACSystems RXi User Manual

Chapter 13. OPC UA Server

OPC UA Performance Considerations

13.9
As mentioned in preceding notes, the OPC UA Server supports 5 concurrent clients and
12,500 addressable elements. Care is suggested both approaching and operating at the
max-max condition: 5 clients accessing the full complement of 12,500 elements
simultaneously.
The OPC UA Server has been designed and implemented to support the maximum number
of clients reading the maximum number of OPC UA elements. However, at maximum load
OPC UA clients may experience degraded performance, evidenced by slower than usual
response times when browsing, reading, and writing addressable elements.
If OPC UA Server response times are not adequate for your application, consider
implementing one or more of the following mitigation strategies:
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 Controller Communications Window – OPC UA traffic is processed in the controller
communications window. If the window's duration is inadequate for the amount of
processing required to service multiple client requests, increasing the comm window
will improve response times by the PLC.
 OPC UA Subscriptions – OPC UA defines a subscription model for the server to
transmit data only when an element's value updates, rather than having a client
continuously poll the server to read an element that is otherwise unchanged in value.
Determine whether your application can use a subscription to collect data from the
PLC.
 OPC UA Aggregating Server – An aggregating server can both allow multiple clients
to connect as a single instance, and combine read-requests for the same element(s)
into one message.
PACSystems* RXi Distributed IO Controller User Manual GFK-2816F