From Systems of Record to Systems of Engagement: Event‑Driven Legacy Modernization with Solace and OpenLegacy

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For decades, enterprises have depended on mainframes and IBM i (AS/400) systems to run their most critical business processes—from core banking and insurance to manufacturing, logistics, and retail. These systems are exceptionally reliable, scalable, and battle‑tested. But they were never designed to operate in a world that expects real‑time insights, cloud agility, AI‑driven intelligence, and event‑driven systems. The result? A growing gap between where the most valuable business data lives and how modern digital systems need to consume it.

Solace and OpenLegacy are closing that gap—together enabling enterprises to modernize legacy systems without rewrites, without disruption, and without risky big‑bang migrations.

The Legacy Modernization Challenge

Despite years of digital transformation initiatives, many enterprises still struggle with the same foundational issues:

Mission‑critical data is locked into mainframe and IBM i systems
Access to that data is tightly coupled to COBOL, CICS, RPG, or green‑screen workflows
Integration relies on batch jobs, polling, file transfers, or point‑to‑point APIs
Event‑driven and real‑time initiatives stall because legacy systems aren’t event‑enabled

Meanwhile, business expectations continue to rise. Customers expect up‑to‑the‑second updates. Operations teams want instant visibility. AI models and analytics platforms require low‑latency, high‑quality data streams—not overnight batch files.

The question is no longer if legacy systems need to participate in modern systems, but how to let them do so safely, incrementally, and at scale.

Making Legacy Systems First‑Class Event Citizens

Solace and OpenLegacy together transform legacy systems of record into real‑time event participants within modern, event‑driven architectures.

Each platform brings a complementary strength:

OpenLegacy specializes in AI-driven, non‑invasive exposure of legacy systems—capturing data changes, business events, and transactions from mainframes and IBM i platforms, with automated service generation
Solace provides the enterprise‑grade event mesh to distribute those events reliably across cloud, on‑prem, and hybrid environments, and increasingly, the backbone for agentic AI applications that require real‑time enterprise data

The result is a powerful modernization pattern: event‑driven coexistence, where legacy and modern systems run side by side, sharing real‑time business events.

The Business Value This Enables

Real‑Time Access to Legacy Data

OpenLegacy captures changes from DB2, DB400, and VSAM and maps them to meaningful, domain‑level business events—such as order.created, account.balance.updated, or policy.status.changed. Solace then distributes these events instantly across the enterprise.

Example: A financial services firm streams real‑time account updates from a mainframe into fraud detection systems and customer‑facing mobile apps—without waiting for batch windows.

Modernization Without Rewrites

Rather than rewriting COBOL or RPG applications, enterprises can modernize incrementally. Legacy systems remain systems of record, while new capabilities are built around them using events.

Example: An insurance provider exposes policy and claims updates as events, enabling digital self‑service portals and real‑time analytics—without touching core policy engines.

Enterprise‑Wide Event Reuse

Once legacy events enter the Solace event mesh, they become reusable enterprise assets. Multiple teams and applications can consume the same events without creating new integrations.

Example: Inventory updates from an IBM i system are consumed simultaneously by supply‑chain planning tools, e‑commerce platforms, partner systems, and analytics dashboards.

AI‑ and Analytics‑Ready Systems

Streaming legacy data into modern platforms unlocks advanced use cases—from real‑time analytics to AI‑driven decisioning.

Example: Manufacturing events from legacy MES systems feed predictive maintenance models and AI agents, enabling proactive issue resolution and operational optimization.

True Coexistence and Phased Migration

Bi‑directional event flows allow modern applications to interact safely with legacy systems. Enterprises modernize domain by domain, without breaking existing workflows.

Example: A retail organization gradually replaces batch‑based order fulfillment with event‑driven microservices—while legacy order processing systems continue to operate normally.

The Art of the Possible

With Solace and OpenLegacy, enterprises can re‑imagine what’s possible with their legacy environments:

Legacy systems driving real‑time digital customer experiences
Mainframe data powering cloud‑native analytics and AI
Event‑driven orchestration across hybrid and multi‑cloud architectures
Gradual domain decoupling without operational risk
Legacy platforms becoming strategic assets, not modernization roadblocks
Legacy events feeding real‑time agentic AI workflows and autonomous decision systems

This is not legacy replacement…it’s legacy evolution.

How It Works

Capturing Legacy Changes and Events: OpenLegacy connects to legacy data stores and transaction systems such as DB2, DB400, and VSAM. Using CDC and transactional hooks, it detects changes and business events in real time—without impacting system performance.
Adding Business Context: Raw data changes are transformed into meaningful, domain‑level events. OpenLegacy applies schemas, validation, and governance so events are immediately consumable by downstream systems.
Publishing into Solace Platform: These events are published into Solace topics, using REST, where they are routed, filtered, and distributed across the enterprise.
Distributing at Scale: Solace ensures secure, reliable delivery across cloud, edge, and on‑prem environments. Teams consume events independently, at their own pace, without tight coupling.
Bi‑Directional Communication (When Needed): Modern applications can also publish events or commands back through Solace. OpenLegacy consumes those events and safely invokes legacy transactions—maintaining governance, validation, and transactional integrity.

A Better Path Forward for Legacy Modernization

Legacy systems aren’t the problem—they’re often the most resilient platforms in the enterprise. The challenge has always been how to connect them to modern, real‑time systems without putting the business at risk.

By combining OpenLegacy’s deep legacy integration capabilities with Solace’s enterprise event mesh, organizations gain a proven, low‑risk path to event‑driven modernization—one that aligns business agility with operational stability.

The future isn’t about abandoning legacy systems, it’s about unlocking their value and letting them lead in a real‑time world.

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Michael Hilmen

Michael Hilmen is senior director of technology in Solace's business development team. With nearly 30 years in the integration and middleware space, he’s worn just about every hat—professional services, sales, engineering, architecture, and business development—across companies ranging from scrappy startups to global giants.

For the past decade at Solace, he's helped enterprises embrace event-driven architecture to reduce the complexity of their system and accelerate the performance of their business. He specializes in showing organizations how EDA forms the backbone of the complex environments it takes to operate efficiently on a global scale.

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