Legacy Databases — Where It All Started

Here is something that surprises most people who are new to technology: the databases running the world right now are older than most of the developers working on them. The system that processes your credit card transaction at the grocery store? It probably runs on technology from the 1970s. The database that holds your Social Security records? Built on a mainframe architecture designed before the moon landing. The software that settles trillions of dollars in stock trades every day? Written in a programming language from 1959.

This is not a failure of the technology industry. It is actually a testament to how well these systems were built. When something works reliably for 40 or 50 years, handling billions of transactions without going down, you do not rush to replace it. You maintain it, you build around it, and you pay very well to keep it running.

This lesson is about those systems — the legacy databases and the ecosystems they created. Understanding them is not just a history lesson. It is a career strategy. There are hundreds of thousands of well-paying jobs maintaining, modernizing, and connecting to these systems. Many of those jobs are right here in Michigan, and they are far less competitive than the trendy startup roles that every bootcamp graduate is chasing.

1. A Timeline of Database History

To understand where we are today, you need to understand how we got here. Database technology has evolved through several distinct eras, each one building on the limitations and lessons of the one before it. Let us walk through the major milestones.

2. Legacy Systems Still Running the World

Let us get specific about the legacy systems that are still in active, heavy production use today. These are not museum pieces. They are the beating heart of the global economy. Understanding what they are, who uses them, and why they persist will help you see career opportunities that most beginners never even consider.

IBM Mainframes and DB2

This is the big one. IBM mainframes process an estimated 68% of the world's production IT workloads. That number is not a typo. More than two-thirds of all production transaction processing happens on mainframe hardware. Every major bank in the world runs core banking operations on IBM mainframes with DB2 databases. When you swipe your debit card, withdraw cash from an ATM, or transfer money between accounts, that transaction almost certainly passes through a mainframe. Insurance companies use mainframes to process claims. Airlines use them for reservation systems. Government agencies — from the IRS to the Social Security Administration — rely on them for their most critical operations.

Mainframes are not just old technology that companies have not gotten around to replacing. They are specifically designed for exactly the kind of work they do: high-volume, high-reliability transaction processing. A single modern mainframe can handle billions of transactions per day with 99.999% uptime (that is less than 5.3 minutes of downtime per year). No other computing platform matches that combination of throughput and reliability for transaction-heavy workloads.

COBOL

COBOL (Common Business-Oriented Language) was created in 1959 — that makes it older than the vast majority of working programmers. Despite its age, COBOL processes an estimated $3 trillion in daily commerce. It runs 95% of ATM transactions, 80% of in-person financial transactions, and a massive share of government benefit systems. The Social Security Administration, the IRS, the Department of Veterans Affairs, and state unemployment systems all rely heavily on COBOL programs running on mainframes.

COBOL is not technically a database, but it is inseparable from the legacy database ecosystem. COBOL programs are the primary interface to DB2 databases on mainframes. They read from and write to these databases, processing the business logic that makes the transactions work. You cannot understand the mainframe world without understanding COBOL, and you cannot work with mainframe databases without encountering it.

The COBOL workforce is aging rapidly. The average COBOL developer is over 50 years old, and many are approaching retirement. This is creating a genuine skills crisis that we will discuss in more detail later in this lesson.

IBM AS/400 (IBM i)

The IBM AS/400 (now officially called IBM i) is one of the most quietly successful platforms in computing history. Released in 1988, the AS/400 was designed as an integrated system where the hardware, operating system, and database (DB2 for i) all work together seamlessly. It was built for mid-market businesses — companies too small for a mainframe but too large for a simple file server.

The AS/400 is legendary for its reliability. Many AS/400 systems have been running continuously for 20 or more years without a reboot. Manufacturing companies, distribution centers, healthcare organizations, and retail chains depend on the AS/400 for their core operations — inventory management, order processing, supply chain logistics, and patient records. These are companies where downtime means the factory stops, shipments do not go out, and patients do not get treated.

The AS/400 world is smaller and less visible than the mainframe world, but the career dynamics are similar: a deep installed base of critical systems, an aging workforce, and a constant need for people who can maintain and modernize these platforms.

Oracle Database

Oracle Database is the dominant commercial relational database in the enterprise world. It is the database of choice for Fortune 500 companies, large government agencies, universities, and healthcare systems. Oracle is known for being extraordinarily powerful, capable of handling enormous databases with complex queries and high transaction volumes. It is also known for being extraordinarily expensive — Oracle licensing can cost hundreds of thousands to millions of dollars per year for large deployments.

That expensive licensing is actually one reason Oracle skills are so valuable. Companies that invest that much money in a database platform need skilled people to manage it. Oracle Database Administrators (DBAs) are among the highest-paid database professionals in the industry. They handle performance tuning, backup and recovery, security, upgrades, and the day-to-day care of databases that often contain an organization's most critical data.

Oracle is also deeply embedded in the enterprise application ecosystem. SAP, PeopleSoft (which Oracle acquired), E-Business Suite, and many other major enterprise applications run on Oracle Database. When a company uses one of these applications, they automatically need Oracle expertise, even if they do not think of themselves as an "Oracle shop."

Microsoft SQL Server

Microsoft SQL Server is the database that grew up with Windows. For companies that built their IT infrastructure on Microsoft technology — Windows servers, Active Directory, .NET applications, SharePoint, and the broader Microsoft ecosystem — SQL Server is the natural database choice. And that describes a huge number of organizations, especially in healthcare, government, education, and mid-sized businesses.

SQL Server has evolved dramatically over the decades. Modern versions include advanced analytics, machine learning integration, cloud hybrid capabilities with Azure, and support for running on Linux. But much of its installed base is still running on older versions, handling the same essential workloads they have managed for years: electronic health records, student information systems, government case management, financial reporting, and thousands of custom line-of-business applications.

SQL Server administration is one of the most accessible paths into database work for beginners. The tooling is excellent (SQL Server Management Studio is one of the best database management interfaces available), the documentation is thorough, there are free learning editions, and the job market is enormous. In the Lansing area and across Michigan, SQL Server jobs outnumber almost any other database specialty.

Sybase (SAP ASE)

Sybase, now known as SAP Adaptive Server Enterprise (SAP ASE) after SAP acquired it, holds a special place in the financial industry. When Wall Street was building out its electronic trading infrastructure in the late 1980s and 1990s, Sybase was the database of choice for its speed and reliability. Many of those trading systems are still running today, and they still run on Sybase.

While the overall market for Sybase has shrunk as organizations migrated to SQL Server, Oracle, or newer platforms, the remaining Sybase installations tend to be extremely critical — the kind of systems where a few seconds of downtime can mean millions of dollars in lost trades. That means Sybase expertise commands premium consulting rates, and organizations with Sybase systems will pay well to keep them running.

Informix (IBM)

Informix, now owned by IBM, was once a major player in the database market. It was particularly popular in retail and manufacturing environments, where its performance characteristics made it well-suited for point-of-sale systems, inventory management, and supply chain operations. While Informix's market share has declined significantly, there is still a meaningful installed base of Informix systems running at retailers, manufacturers, and telecommunications companies.

Like other legacy database platforms, Informix creates career opportunities precisely because fewer people learn it. If you encounter an organization running Informix, having even basic familiarity with it puts you in a small and valuable group of people who can help.

3. Why Legacy Systems Persist

If newer technology is available, why don't organizations just upgrade? This is one of the most important questions in enterprise technology, and the answer reveals a lot about how real-world business works. There are several powerful forces that keep legacy systems in place, and understanding them will help you navigate the professional world more effectively.

Proven Reliability

The single biggest reason legacy systems persist is that they work. A mainframe that has been processing ATM transactions for 30 years with 99.999% uptime has earned an enormous amount of trust. When you are talking about systems that handle money, medical records, or government benefits, "it works and has always worked" is an incredibly powerful argument against changing anything. No executive wants to be the person who replaced a perfectly working system and caused a catastrophe.

The Risk of Migration

Migrating from a legacy system to a modern one is one of the most dangerous things an organization can do. These systems have accumulated decades of business logic — thousands of rules, edge cases, and behaviors that were added one at a time over many years. Some of that logic is not documented anywhere except in the code itself. Moving it to a new platform means understanding and replicating every single rule, and getting even one wrong can have serious consequences. Failed database migrations have caused banks to lock customers out of their accounts, airlines to ground entire fleets, and government agencies to stop processing benefits. These high-profile failures make other organizations even more cautious about attempting migration.

Institutional Knowledge Loss

The people who built these systems and understand them best are retiring. When they leave, they take irreplaceable knowledge with them — knowledge about why a particular business rule exists, what happens if you change a specific parameter, or how two systems interact in ways that are not documented anywhere. This knowledge loss makes migration even riskier, because the people who could safely guide a transition are no longer available.

The True Cost of Replacement

Replacing a legacy system is staggeringly expensive. A major bank migrating off a mainframe might spend hundreds of millions of dollars over several years. And that is just the technology cost — it does not include the cost of retraining staff, updating processes, testing, and the risk of things going wrong during the transition. For many organizations, the cost of maintaining the legacy system, even with expensive specialized talent, is a fraction of the cost of replacing it.

Regulatory and Compliance Requirements

Banks, healthcare organizations, and government agencies operate under strict regulatory frameworks. Any system change has to be validated, documented, and often approved by regulators. For a major database migration, this compliance process alone can take years. In heavily regulated industries, the regulatory burden of changing systems is sometimes as expensive and time-consuming as the technical work itself.

4. Career Implications — Where the Jobs Are

Now let us talk about what all of this means for your career. The legacy database landscape creates a wide variety of job opportunities across different sectors, and many of these opportunities are more accessible to career changers and self-taught developers than you might expect. Let us go through each sector in detail.

Enterprise / Fortune 500

Large corporations are the biggest employers of database professionals, and the vast majority of them rely on legacy database systems. Oracle DBAs and SQL Server administrators are in constant demand at these companies, and the need never really goes away because the databases they manage are running 24/7, growing in size, and constantly requiring tuning, patching, and support.

Financial services is one of the most database-intensive industries. Banks, insurance companies, credit unions, and investment firms maintain enormous databases of customer accounts, transaction histories, policy records, and regulatory data. JPMorgan Chase, Bank of America, Comerica (headquartered in Dallas but with significant Michigan operations), and every other major bank all need database professionals. Insurance companies like Blue Cross Blue Shield, Auto-Owners Insurance (based right here in Lansing), and Accident Fund are constantly hiring people who can work with their data systems.

Healthcare runs on databases. Electronic health record (EHR) systems like Epic and Cerner store every patient encounter, every lab result, every prescription, and every billing record in massive databases — usually Oracle or SQL Server. Hospitals, health systems, and healthcare technology companies need database administrators, data analysts, and developers who can work with these systems. Sparrow Health System (now part of University of Michigan Health) right here in Lansing runs these exact kinds of systems.

Telecom companies like AT&T, Verizon, and T-Mobile manage billions of call records, customer accounts, and network performance metrics in legacy databases. Retail giants like Meijer (Michigan-based), Kroger, and Walmart use legacy database systems for inventory management, supply chain logistics, and point-of-sale data. Manufacturing companies, which Michigan has in abundance, use databases to track production schedules, quality control, parts inventories, and shipping logistics.

Government (Federal, State, and Local)

Government at every level is one of the largest users of legacy database technology, and it is one of the most stable employers for database professionals.

Federal agencies operate some of the oldest and most critical legacy systems in existence. The IRS processes tax returns for over 150 million Americans using systems built on mainframes and COBOL programs that date back to the 1960s. The Social Security Administration manages benefits for 70 million Americans on similar legacy infrastructure. The Department of Veterans Affairs, the Department of Defense, and dozens of other agencies all depend on decades-old database systems for their core operations. These agencies are constantly hiring people who can maintain, secure, and gradually modernize these systems.

State government is closer to home and often overlooked as a career path. The State of Michigan runs its core operations on a combination of mainframe systems, Oracle databases, and SQL Server databases. The Department of Health and Human Services, the Secretary of State's office, the Department of Treasury, and the Unemployment Insurance Agency all depend on legacy database systems. During the early months of the COVID-19 pandemic, Michigan's unemployment system — built on decades-old COBOL and mainframe technology — had to process an unprecedented surge in claims, highlighting both the fragility and the absolute criticality of these systems. The state is actively hiring people who can work with this technology.

Local government — cities, counties, and school districts — also relies on databases for everything from property tax records to utility billing to court case management. The City of Lansing, Ingham County, Lansing School District, and Michigan State University all maintain database systems that need professional support.

Government IT work comes with significant benefits: competitive salaries, excellent health insurance, retirement pensions, generous paid time off, job stability that private sector jobs often cannot match, and the satisfaction of working on systems that serve the public. For someone building a career and raising a family in the Lansing area, government database work is a path worth serious consideration.

Consulting and System Integrators

Some of the biggest companies in the world make their money helping other organizations modernize their legacy technology. Deloitte, Accenture, IBM Consulting, Infosys, Wipro, and dozens of other consulting firms employ armies of consultants who specialize in understanding legacy systems and building bridges to modern technology. This is a multi-billion-dollar industry.

What makes consultants valuable is the ability to understand both the old and the new. A consultant who can look at a 30-year-old COBOL application running on DB2, understand what it does, and then design a migration path to a modern Java application with a cloud database is worth an enormous amount of money. These consulting projects can last years, and they pay well at every level of seniority.

Consulting is also an excellent way to learn quickly. In a consulting role, you might work on projects at a bank, then a healthcare company, then a government agency — each one exposing you to different systems, industries, and challenges. After a few years in consulting, you will have a breadth of experience that is hard to match in a single-employer role.

Startups

At first glance, startups seem like the opposite of legacy technology. Startups build new products with new technology — they use PostgreSQL, MongoDB, cloud databases, and the latest frameworks. They almost never use mainframes, COBOL, or DB2 directly. So why should you care about legacy databases if you want to work at a startup?

Because many of the most successful startups sell to enterprises that do. This is especially true in three of the hottest startup sectors:

• Fintech (financial technology): Startups like Stripe, Plaid, and Square build products that connect to banks. Those banks run on legacy databases. Understanding how legacy systems work helps you build products that integrate with them.
• Healthtech (healthcare technology): Startups building tools for hospitals and clinics need to integrate with electronic health record systems that run on Oracle and SQL Server. Understanding the legacy data models and compliance requirements of healthcare gives you a major advantage.
• Govtech (government technology): Startups like Nava PBC and Bloom Works build modern interfaces for government services. The data those services need lives in legacy databases on mainframes. Startups that hire people who understand both sides have a massive competitive advantage in winning government contracts.

Even if you dream of working at a startup, understanding legacy systems makes you more valuable because you can be the bridge between the startup's new technology and its customers' old technology.

The COBOL Opportunity

This deserves its own section because the career dynamics are so unusual. COBOL is a 65-year-old programming language that most computer science programs stopped teaching decades ago. And yet it runs critical infrastructure that processes trillions of dollars every day. The people who know COBOL are retiring. The pipeline of new COBOL developers is essentially empty. The result is a classic supply-and-demand imbalance that creates real opportunity.

Experienced COBOL contractors regularly bill at $100 to $150 or more per hour. During the pandemic, when state unemployment systems built on COBOL were overwhelmed, several states issued public pleas for COBOL programmers and were willing to pay premium rates. New Jersey's governor literally went on live television and asked for COBOL volunteers.

The average COBOL developer in the workforce is over 50 years old. Within the next 10 to 15 years, a massive portion of the COBOL workforce will retire. The systems they maintain are not going away — they are too critical to shut down and too risky to replace quickly. This means someone has to learn COBOL and take over. Some organizations have recognized this and are now paying to train junior developers in COBOL and mainframe technology, sometimes through apprenticeship programs with full salaries during training.

Is COBOL glamorous? No. Will you impress people at tech meetups by saying you write COBOL? Probably not. But will you have stable, well-paying work for as long as you want it? Almost certainly yes. For someone starting a career in the Lansing area who values stability and good compensation over trendy technology, COBOL is one of the most practical paths available.

5. The Legacy-to-Modern Bridge

One of the most interesting career positions you can occupy is the person who understands both legacy and modern technology. Organizations desperately need people who can bridge the gap between their old systems and the new tools they want to adopt. This bridging work is some of the most valuable and well-compensated work in the technology industry.

Java/Spring Boot as the Bridge

If you have been following the Coders Farm curriculum, you have already started learning Java and Spring Boot. This is not a coincidence. Java is the single most common language used to modernize legacy systems. Here is why:

• Enterprise adoption: Java has been the dominant enterprise programming language for over 25 years. Virtually every large organization already has Java expertise, Java applications, and Java infrastructure. When a company wants to modernize a legacy system, Java is almost always on the short list of target technologies.
• Spring Boot: Spring Boot makes it relatively straightforward to build modern REST APIs and microservices that can connect to legacy databases. You can create a Spring Boot application that reads from a DB2 database on a mainframe, transforms the data, and exposes it through a modern API that web and mobile applications can consume. This pattern — wrapping legacy data in modern APIs — is one of the most common modernization strategies in the industry.
• JDBC connectivity: Java's JDBC (Java Database Connectivity) standard provides a consistent way to connect to almost any database, legacy or modern. The same Java code can talk to Oracle, SQL Server, DB2, MySQL, and PostgreSQL with minimal changes. This makes Java the natural choice for building applications that need to work with multiple database systems simultaneously.

Being the person who can write a Spring Boot API that connects to a legacy DB2 database and serves data to a modern React frontend is incredibly valuable. You are the translator between two worlds, and both sides need you.

6. Legacy Database Comparison

Here is a reference table that summarizes the legacy database systems we have discussed. Keep this handy — when you encounter these names in job postings, conversations, or technical discussions, you will know exactly what they are and where they fit in the landscape.

Test Your Knowledge

Let us check that the key ideas from this lesson are sticking. Answer the questions below.

Lesson Summary

In this lesson, you learned that the technology running the world's most critical systems is far older than most people realize. You walked through the history of databases from flat files in the 1960s to the NoSQL revolution of the 2000s, and you saw that no era of database technology has truly replaced the one before it. Instead, each new generation adds to the landscape while previous generations continue serving their critical roles.

You learned about the specific legacy systems still in heavy production use: IBM mainframes and DB2 processing 68% of production workloads, COBOL handling $3 trillion in daily commerce, the AS/400 running manufacturing and distribution with legendary reliability, Oracle dominating the Fortune 500, SQL Server powering the Windows enterprise world, Sybase underpinning Wall Street, and Informix serving retail and manufacturing.

You explored why these systems persist — not because organizations are ignorant of modern technology, but because proven reliability, migration risk, knowledge loss, replacement cost, and regulatory requirements make it rational to keep them running. And you saw how this creates real career opportunities across enterprise, government, consulting, startups, and the COBOL talent market specifically.

Most importantly, you learned a truth that will serve you throughout your career: SQL is about 90% the same everywhere. The skills you are building right now transfer across every relational database system, from the oldest mainframe to the newest cloud database. And the person who understands both old and new technology — who can bridge the gap between a 1970s mainframe and a 2020s cloud application — is one of the most valuable people in any organization.

"The developer who understands legacy systems and modern systems is not just twice as valuable — they are ten times as valuable, because they are the bridge that makes modernization possible."