Legacy System Integration Methods

Most would agree that building a brand-new house is significantly easier than carrying out a major renovation on an old one. The same principle applies to control systems. Setting up a new system is often much simpler than upgrading an existing one. When it comes to major upgrades, especially for Distributed Control Systems (DCS), there are 8 elements that must be carefully considered to ensure a successful implementation: 1. System Compatibility & Integration • Legacy System Interface: Ensure new DCS can interface with older field instruments, I/O modules, and control logic (if retained). • Protocol Mismatch: Compatibility between old and new communication protocols (e.g., HART, Profibus, Foundation Fieldbus, Modbus). • Third-party System Integration: SCADA, PLCs, SIS (Safety Instrumented Systems), historians, and asset management tools must seamlessly integrate. 2. Downtime Minimization • Phased Migration Plan: Design must allow partial switchover to maintain plant operations. • Hot Cutover Capability: Ensure some systems can switch without shutting down the entire plant. • Backup Systems: Redundant systems and fallback strategies in case of failure during the upgrade. 3. Cybersecurity • Hardening the New System: New DCS introduces network exposure; firewalls, segmentation, and intrusion detection must be included. • Patch Management: Choose systems with secure patching and vendor support. • Compliance: Meet standards like ISA/IEC 62443. 4. Safety Systems Interface • SIS Independence: Ensure the DCS upgrade doesn’t compromise the independence and integrity of Safety Instrumented Systems. • Interlock Revalidation: All interlocks and safety logics must be retested and validated post-upgrade. 5. Data Migration & Configuration • Control Logic Transfer: Rewriting or translating existing logic into the new system format without losing functionality. • Historian & Alarm Data Migration: Maintain data integrity during transfer. • I/O Mapping Accuracy: Critical to ensure correct connections between field devices and control logic. 6. Hardware & Network Architecture • Redundancy Design: Controller, power, and network redundancy for high availability. • Scalability: Room for future expansion in the control system design. • Segmentation: Proper zoning of control and field networks for performance and security. 7. Operator Interface & HMI Design • Operator Familiarity: Reduce the learning curve with intuitive graphics and control layouts. • Alarm Rationalization: Avoid alarm flooding; ensure alarm priorities are re-evaluated. • Simulation & Training: Include an operator training simulator for commissioning and operational transition. 8. Compliance & Validation • Documentation: Thorough as-built and functional documentation for audits and training. • Regulatory Standards: Compliance with API, OSHA, ISA, and local regulations.

Publishing Events from Legacy Why? To give legacy bragging rights? You know, some of that latent coolness. The reason events are published out of a legacy system should be to provide a means of integration and to incrementally modernize/transform. The alternative is to jump into the existing legacy code and start teasing apart the tangle for the purpose of modularizing the monolith. I know that's possible because I've done it with very large codebases. Yet picking off small facts of happenings in the legacy is very effective and arguably much simpler. I've used both approaches, spoken and written about, and taught them. Some claim that using events at all is due to the influence of Kafka. Is that true? It wasn't for me. Although Kafka may be involved in enabling this approach, it has nothing to do with the motivation. Domain Events and my use of them significantly predate Kafka. Surprisingly, publishing events from legacy can require little to no legacy source code modification. Instead, you use a stream of database changes and reify transaction log entries to events, which then are published via a messaging mechanism. It may or may not be Kafka. If you are interested in learning more about this, see the OSS product Debezium. This will be the topic of my next Design Accelerator episode.

𝗜𝗻𝘁𝗲𝗴𝗿𝗮𝘁𝗶𝗻𝗴 𝗖𝗹𝗼𝘂𝗱-𝗡𝗮𝘁𝗶𝘃𝗲 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲𝘀 𝘄𝗶𝘁𝗵 𝗟𝗲𝗴𝗮𝗰𝘆 𝗦𝘆𝘀𝘁𝗲𝗺𝘀: 𝗟𝗲𝘀𝘀𝗼𝗻𝘀 𝗳𝗿𝗼𝗺 𝘁𝗵𝗲 𝗙𝗶𝗲𝗹𝗱 In a recent engagement with a large financial services company, the goal was ambitious: 𝗺𝗼𝗱𝗲𝗿𝗻𝗶𝘇𝗲 𝘀𝘆𝘀𝘁𝗲𝗺𝘀 𝗼𝗳 𝗲𝗻𝗴𝗮𝗴𝗲𝗺𝗲𝗻𝘁 𝘁𝗼 𝗽𝗿𝗼𝘃𝗶𝗱𝗲 𝗮 𝗰𝘂𝘁𝘁𝗶𝗻𝗴-𝗲𝗱𝗴𝗲 𝗰𝘂𝘀𝘁𝗼𝗺𝗲𝗿 𝗲𝘅𝗽𝗲𝗿𝗶𝗲𝗻𝗰𝗲. 𝙏𝙝𝙚 𝙘𝙖𝙩𝙘𝙝? Much of the critical functionality resided on mainframes—reliable but inflexible systems deeply embedded in their operations. They needed to innovate without sacrificing the stability of their legacy infrastructure. Many organizations face this challenge as they 𝗯𝗮𝗹𝗮𝗻𝗰𝗲 𝗺𝗼𝗱𝗲𝗿𝗻 𝗰𝗹𝗼𝘂𝗱-𝗻𝗮𝘁𝗶𝘃𝗲 𝗮𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲𝘀 𝘄𝗶𝘁𝗵 𝗹𝗲𝗴𝗮𝗰𝘆 systems. While cloud-native solutions promise scalability and agility, legacy systems remain indispensable for core processes. Successfully integrating these two requires overcoming issues like 𝗴𝗼𝘃𝗲𝗿𝗻𝗮𝗻𝗰𝗲, 𝗰𝗼𝗻𝘁𝗿𝗼𝗹, and 𝗰𝗼𝗺𝗽𝗮𝘁𝗶𝗯𝗶𝗹𝗶𝘁𝘆 𝗴𝗮𝗽𝘀. Drawing from that experience and others, here are 📌 𝟯 𝗯𝗲𝘀𝘁 𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲𝘀 I’ve found valuable when integrating legacy functionality with cloud-based services: 𝟭 | 𝗔𝗱𝗼𝗽𝘁 𝗮 𝗛𝘆𝗯𝗿𝗶𝗱 𝗠𝗼𝗱𝗲𝗹 Transition gradually by adopting hybrid architectures. Retain critical legacy functions on-premises while deploying new features to the cloud, allowing both environments to work in tandem. 𝟮 | 𝗟𝗲𝘃𝗲𝗿𝗮𝗴𝗲 𝗔𝗣𝗜𝘀 𝗮𝗻𝗱 𝗠𝗶𝗰𝗿𝗼𝘀𝗲𝗿𝘃𝗶𝗰𝗲𝘀 Use APIs to expose legacy functionality wherever possible and microservices to orchestrate interactions. This approach modernizes your interfaces without overhauling the entire system. 𝟯 | 𝗨𝘀𝗲 𝗘𝗻𝘁𝗲𝗿𝗽𝗿𝗶𝘀𝗲 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 𝗧𝗼𝗼𝗹𝘀 Enterprise architecture tools provide a 𝗵𝗼𝗹𝗶𝘀𝘁𝗶𝗰 𝘃𝗶𝗲𝘄 of your IT landscape, ensuring alignment between cloud and legacy systems. This visibility 𝗵𝗲𝗹𝗽𝘀 𝘆𝗼𝘂 𝗰𝗼𝗺𝗺𝘂𝗻𝗶𝗰𝗮𝘁𝗲 with Product and Leadership to prioritize initiatives and avoid redundancies. Integrating cloud-native architectures with legacy systems isn’t just a technical task—it’s a strategic journey. With the right approach, organizations can unlock innovation while preserving the strengths of their existing infrastructure. _ 👍 Like if you enjoyed this. ♻️ Repost for your network.  ➕ Follow @Kevin Donovan 🔔 _ 🚀 Join Architects' Hub!  Sign up for our newsletter. Connect with a community that gets it. Improve skills, meet peers, and elevate your career! Subscribe 👉 https://lnkd.in/dgmQqfu2 Photo by Raphaël Biscaldi  #CloudNative #LegacySystems #EnterpriseArchitecture #HybridIntegration #APIs #DigitalTransformation

"Replacing Legacy Systems, One Step at a Time with Data Streaming: The Strangler Fig Approach" Modernizing #legacy systems does not need to mean a risky big bang rewrite. Many enterprises are now embracing the #StranglerFig Pattern to migrate gradually, reduce risk, and modernize at their own pace. When combined with #DataStreaming using #ApacheKafka and #ApacheFlink, this approach becomes even more powerful. It allows: - Real time synchronization between old and new systems - Incremental modernization without downtime - True decoupling of applications for scalable, cloud native architectures - Trusted, enriched, and governed data products in motion This is why organizations like #Allianz are using data streaming as the backbone of their #ITModernization strategy. The result is not just smoother migrations, but also improved agility, faster innovation, and stronger business resilience. By contrast, many companies have learned that #ReverseETL is only a fragile workaround. It introduces latency, complexity, and unnecessary cost. In today’s world, batch cannot deliver the real time insights that modern enterprises demand. Data streaming ensures that modernization is no longer a bottleneck but a business enabler. It empowers organizations to innovate without disrupting operations, migrate at their own speed, and prepare for the future of event driven, AI powered applications. Are you ready to transform legacy systems without the risks of a big bang rewrite? Which part of your legacy landscape would you “strangle” first with real time streaming, and why? More details: https://lnkd.in/erxrBJNn

Bridging the Gap: The Adapter (Wrapper) Pattern in .NET Ever tried connecting two incompatible systems or libraries in a project? That’s where the Adapter Pattern shines. Also known as the Wrapper, this design pattern acts as a translator, enabling classes with incompatible interfaces to work together seamlessly. When to use it: • Integrating third-party libraries with your existing code. • Unifying different APIs under a common interface. • Migrating legacy systems to modern ones without rewriting everything. Pros: • Encourages code reuse without modifying the original classes. • Provides a clear boundary between new and legacy code. Cons: • May introduce additional complexity. • Can lead to performance overhead if overused. Have you ever used the Adapter Pattern in your projects? What challenges did you face? #DesignPatterns #CSharp #SoftwareDevelopment #CleanArchitecture #SoftwareEngineering