Legacy application modernization is a significant aspect of any business’s IT modernization strategy. A successful application modernization strategy must include a perspective of what business value is being created by the transformation. The tangible benefits realized by most businesses can be attributed to many improvements, for example:

  • Faster IT Delivery
  • Increased Reliability
  • Increased Performance Quality
  • Create Capability for Application Upgrades
  • Avoid Business Disruptions

What Are Legacy Applications

As a business operates it acquires applications for performing tasks that create value. Over time those applications become antiquated, stuck on unsupported infrastructure, and limited in future development. The term “Legacy” is used to describe applications both to acknowledge the business value they create and to acknowledge the aging nature of the application.

If an application continues to generate value, the business should expect IT to maintain it. Over time maintaining legacy applications becomes more difficult for a variety of reasons. From an IT perspective here are three examples:

  • The original resources responsible for owning, developing, and configuring the applications have long moved on.
  • Lack of vendor support for developing legacy applications.
  • Constantly increasing demand on IT to prevent cyber-attacks on legacy applications.

Given enough time almost all types of applications used by businesses will eventually grow to become legacy applications.

What Is A Legacy System Migration

A legacy system migration is the component of an IT modernization process where applications are moved from their old hardware to newer hardware with a supported platform.

A common mistake for businesses is to procrastinate modernizing essential business applications until they are forced to. Unfortunately, legacy applications are more difficult to modernize the longer a business has delayed the effort. The increased complexity associated with the app migration only further delays modernization and rarely does the growing complexity spur modernization. Instead, business is usually driven by one of the few following triggers to initiate a modernization project.

What Are The Final Triggers For Businesses That Initiate A Legacy Application Migration

  1. Cyber Attacks
  2. The Operating System Is No Longer Supported
  3. Regulatory Compliance
  4. Security Vulnerabilities
  5. Application Upgrades Are No Longer Supported
  6. Barriers Integrating Legacy Application
  7. End Of Extended Support
  8. Server Capacity

Why Are Legacy Applications Migrated

The best practice for modernizing legacy applications is to first upgrade the environment they are installed on to a supported version of the operating system.

Leaving applications installed in an unsupported environment is rarely an acceptable modernization practice. Legacy environments are just not secure for business applications in a production environment. Those security concerns may also be further exasperated by regulatory compliance.

There are many benefits to migrating legacy applications to a modern operating system. Migrated legacy applications will see their expected lifecycle extended. Frequently the hardware is upgraded because of the migration, which serves as a platform for other improvements. Stack components such as IIS and SQL Server can also easily be upgraded while migrating applications to a newer operating system. There is also the option of migrating the applications to the cloud which unlocks many upgrade paths.

Is The Cost Of Windows Server Extended Support Worth It

Microsoft’s Extended Support is an invaluable tool for when critical business applications have not been migrated within the supported window. The first path most businesses will consider before a modernization strategy is Microsoft’s Extended Support. Extended Support is a paid service provided by Microsoft for roughly 5 years following the end of mainstream support for an operating system.

At the end of Extended Support best practices are for businesses to have modernized or decommissioned their legacy servers. In the case of extremely valuable or critical applications that remain on legacy servers, a business will need to consider purchasing Microsoft’s Beyond End-of-Support at a significant cost.

Extended Support is an invaluable resource, but the business doesn’t generate any value from the money put into it. Extended Support is only the cost to defer IT modernization, it is not an investment in IT modernization. The best practice is to keep up-to-date modernizing your server architecture and utilize extended support only when needed.

5 Steps To Modernize Your Legacy Applications

  1. Inventory Applications
  2. Evaluate Legacy Applications For Modernization
  3. Determine The Modernization Strategy For Each Application
  4. Prepare Destination Environments
  5. Execute Application Migrations

Evaluating Legacy Applications For Migration

A business has five strategies to use for modernizing its applications. Different modernization strategies will be applied for each specific application. Determining which strategy is appropriate for each application requires first an inventory and second an assessment of the business’s applications.

Step 1 can also be referred to as Application Discovery. During the application discovery process, a business should develop a clear understanding of its applications and their dependencies. Migration Intelligence tools exist to automate the otherwise manual task. Another benefit of using Migration Intelligence is the detailed documentation generated for each application.

Step 2 will require the business to examine and evaluate each application. A scorecard or platform should be developed to assess the IT and Business value driving the migration effort of each application. Based on the business’s assessment of each application’s value, an appropriate modernization strategy will be selected.

Business & IT Drivers Behind Legacy Application Modernization

Business Drivers:


  • Does the legacy application continue to fulfill the business’s current requirements?
  • Has there been quality or reliability concerns related to the application?


  • What value does the legacy application create?
  • How essential is the application to business operations?

Agility – can your legacy application keep pace with today’s digital demands?

  • What is the expected value of the modernized application
  • Where is the application holding you back

IT Drivers:


  • What is the current cost to maintain the legacy application?
  • What is the projected savings of modernizing the application?
  • What is the cost of migrating the legacy application?


  • What complexity is associated with the application?
  • What knowledge and documentation do we have of the application?
  • Are there particular complexities to migrating this application?


  • What are the security implications of the application remaining on an unsupported OS?
  • Does the application threaten business: security, compliance, operations, or data?

Five Strategies To Modernize Legacy Applications

  1. Rehost (Lift and Shift)
  2. Replatform (Lift, Shift, and Tinker)
  3. Refactor (Rearchitect)
  4. Replace (Repurchase)
  5. Retire (Decommission)

A business will make use of many or all the app modernization strategies throughout an IT modernization effort. Different strategies will be executed for different applications. The first three modernization strategies listed involve migrating the legacy applications. The final two strategies focus on replacing or decommissioning the legacy application.