Future-Proofing Connectivity

OPC DA vs. OPC UA Integration with AVEVA PI System

PT Scada Prima Cipta — AVEVA / Schneider Electric System Integrator

Choosing the connectivity method between an industrial control system and AVEVA PI System is a long-term architecture decision. It shapes cybersecurity posture, data reliability, maintainability, and an organization's readiness for digital transformation.

1. Why OPC Integration Matters for PI System

AVEVA PI System is widely used as an enterprise historian, collecting process data from PLCs, DCSs, SCADA systems, and other operational platforms. For that data to reach the PI Server, a communication mechanism such as OPC DA or OPC UA is required.

2. OPC DA: A Legacy Solution Still Widely Used

OPC DA (Data Access) is a mature technology built on Microsoft's COM/DCOM framework. It has been used across industry for decades, so a large installed base of existing systems still relies on it.

Strength: proven stability across thousands of industrial installations, with certain redundancy configurations supported.
Strength: PI Interface for OPC DA provides interface and OPC-server failover mechanisms.
Limitation: requires complex DCOM configuration (dynamic RPC ports, identity and permission settings on both nodes).
Limitation: harder to secure at the network level — multiple firewall rules are typically needed, and DCOM has no native encryption.

3. OPC UA: The Modern Industry Standard

OPC UA (Unified Architecture) was designed to overcome OPC DA's limitations. First released by the OPC Foundation in 2006 (version 1.00) and later ratified internationally as IEC 62541 in 2010, it uses a modern TCP/IP-based protocol together with certificate-based security and encryption, making it easier to deploy in modern IT/OT architectures.

Strength: security built on X.509 certificates, message signing, and encryption.
Strength: single TCP endpoint (opc.tcp://) that is much simpler to pass through a firewall than DCOM's dynamic ports.
Strength: the natural choice for new projects and for integration with cloud/enterprise platforms.

Consideration: administration and redundancy features differ from the traditional PI Interface model — PI System collects OPC UA data through the PI Connector for OPC UA (available since 2016) or the newer AVEVA Adapter for OPC UA, both of which use an intermediate relay component (PI Connector Relay / PI Web API) rather than a direct DCOM-style connection.

4. OPC DA vs. OPC UA in AVEVA PI System — Comparison

5. Architecture Selection Guide

Use a PI Connector / AVEVA Adapter for OPC UA when:

The project is greenfield.
The PLC/DCS/SCADA already exposes a native OPC UA server.
Cybersecurity and IT/OT integration are the top priorities.

Use PI Interface with OPC DA when:

The existing system still runs on OPC DA.
A proven, field-tested redundancy mechanism is required.
A full migration to OPC UA is not yet feasible.

6. Migration Strategy from OPC DA to OPC UA

Migration does not need to happen all at once. A phased approach is generally safer:

Assess all existing OPC data sources.
Identify which devices already support OPC UA natively.
Use an OPC UA wrapper/gateway for older devices that only expose OPC DA.
Migrate tags incrementally, validating data quality at each step.
Maintain redundancy and buffering throughout the transition period.

7. Conclusion

OPC DA remains a valid choice for legacy environments with proven high-availability requirements. For long-term investment, however, OPC UA provides a stronger foundation for cybersecurity, IT/OT integration, and digital transformation — reinforced by its status as the IEC 62541 international standard.

General recommendation: use OPC UA for greenfield projects. For brownfield systems, evaluate risk carefully before migrating, especially for critical systems that demand high availability.

Comparing OPC DA and OPC UA integration paths for AVEVA PI System — here's what matters most before you choose. 👇

🔹OPC DA: flexible data collection, fault-tolerant/redundant support — but a wider firewall footprint
🔹OPC UA: certificate-secured, single-port design — but no redundancy, no in-place tag editing

🔹Quick guide: