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--- tanszek:oktatas:iss_t:software_integration [2026/02/22 11:05] – [Legacy Systems] knehez
+++ tanszek:oktatas:iss_t:software_integration [2026/02/22 11:15] (current) – [Example] knehez
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   * __Gradual migration__: instead of replacing the entire system at once, organizations incrementally migrate to new systems by replacing specific components or functionalities.
   * __Outsourcing maintenance and operation__: maintenance and operation of legacy systems may be delegated to external service providers, reducing internal costs and specialized staffing requirements.
+==== Interesting Real-World examples of Legacy Systems ====
+In many cases, legacy systems serve as the backbone of critical global infrastructure. Some of the most striking examples can be found in the financial sector. Major institutions such as //JPMorgan Chase// and //Bank of America// still rely heavily on __COBOL-based__ core banking systems running on __IBM mainframes__. COBOL, introduced in 1959, remains responsible for processing an enormous portion of the world’s financial transactions. During the __COVID-19__ pandemic, the continued reliance on COBOL became apparent to the broader public when U.S. government agencies urgently sought experienced COBOL developers to maintain unemployment benefit systems.
+Another remarkable case is the __airline reservation infrastructure__ originally developed for American Airlines in cooperation with IBM in the early 1960s. The SABRE system was one of the earliest large-scale real-time transaction processing systems. Although it has undergone continuous modernization, elements of its original architecture still influence its operation today. The system handles millions of transactions daily and demonstrates how evolutionary development can preserve legacy foundations while incrementally adapting to new technological requirements.
+__Public administration__ also provides compelling examples. The U.S. Internal Revenue Service (IRS) continues to operate tax processing systems that date back to the 1960s. Despite multiple large-scale modernization programs costing billions of dollars, complete replacement has proven extremely complex due to regulatory constraints, security requirements, and the critical importance of uninterrupted service.
+In transportation infrastructure, legacy technology can even affect physical operations. Parts of the London Underground’s signaling and control systems have historically relied on hardware and software developed decades ago. In some cases, replacement components had to be sourced from secondary markets because original manufacturers no longer produced them. Such situations illustrate not only software legacy issues but also hardware obsolescence and supply chain risks.
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     DB2 -- read --> B2
 </mermaid>
-==== Example ====
+Example: E-commerce platform and Warehouse Management System:
-E-commerce platform and Warehouse Management System:
 The e-commerce platform can be directly integrated with the warehouse database to provide real-time inventory information.