The Biggest Challenges of Legacy Modernization (and How to Avoid Them)


Making a big jump forward from legacy software is always hard. It's difficult enough when doing it at a reasonable pace, but it's worse when circumstances force a transition. Even if a deadline is looming, a successful legacy migration requires a systematic approach. Rushing the job in a panic will only make it harder.

The challenges of legacy modernization include both technical and human issues. The transition has to reach completion without breaking anything (which is obviously necessary). That includes effective workflows as well as compatible functionality.

The Reasons for Migration

A migration plan should start with a clear understanding of what constitutes the end goal. This provides a standard for measuring the success of the process. It also helps to identify where the risks are. These are some of the most common reasons a migration is necessary:

  • The vendor no longer supports the old software. Bugs will no longer be fixed, and it may not run properly under future operating system code. If the software was developed internally, the people who understand it may no longer be there, or the effort of keeping it working could be too great.
  • The business wants to move to a cloud system or to new hardware. The legacy software may run only on legacy computers.
  • The software can no longer satisfy new needs for functionality or compliance.
  • It doesn't work well with other software which has been upgraded or newly implemented.

Some upgrades may be for custom software, written especially for the company. Others are for software which already exists commercially. These are at two ends of a continuum, and with either situation, there's always some development work to do. An upgrade to software which is already available will generally require some custom coding for importing data, tailoring the user interface, or adding custom functionality.

Broadly speaking, there are two types of challenges of legacy modernization. There are technical issues, relating to functionality, interfaces, and compatibility. There are also user issues, concerning the software's usability and acceptance.

Technical Challenges

Data Migration

If the new software can handle the legacy software's data with no changes, that's a huge help. More often, there are data compatibility issues. They could be subtle ones that no one recognizes at first.

Individual fields may cause issues. The format of dates or currency amounts could be different. The old software might have full names in one field while the new one wants separate first, last, and middle names.

Missing data is also a frequent source of aggravation. The legacy software may make assumptions about blank fields which are different from the new code's interpretation. There might be a difference between a missing and a blank field, or not. The data might include bad fields which the legacy software cheerfully ignores. It may be necessary to generate new indexes and unique identifiers.

Data cleanup can become a project in itself before the migration can proceed. (Those of you who have been through this process can attest to this fact.)


The documentation for a legacy system is often incomplete, inaccurate, or simply missing. Documentation of the internals is generally the worst. It can essentially be a 'black box' of sorts. There may be features which are essential to current operations but aren't documented. Not knowing exactly what the existing system does makes it hard to preserve its functionality in the upgrade.

Integration with Other Tools

Software rarely operates in complete isolation. It usually exchanges information with other tools that the business uses. Both sides have to agree on a protocol or API. Either the replacement software has to match the legacy software in exchanging information, or the other tools have to adapt. Sometimes several tools need to be updated at once to keep everything working.

Dependencies on Other Software

If the legacy software uses services to get or store data or to make network connections, the replacement code has to do the equivalent. This may require writing adapters for the upgrade code. It may require changing the way the services work. The issues are similar to data migration, but they're ongoing rather than a one-time conversion.

Human Challenges

Some of the challenges which turn up in an upgrade are better classified as "people issues" rather than technical ones. Some challenges may have technical solutions, but others are more a matter of good communication and training.

When people are familiar with a system, they don't like change unless they're facing serious problems. Getting them to accept the new software will take some effort. Presentations and materials showing how the upgrade will make their jobs easier will help.

Sometimes it's not just a matter of disliking change. The existing system may fit their workflow very well. The new one, even if its features are individually better, won't always work as smoothly with processes which employees have used for years. If the upgrade isn't a good fit, it could reduce productivity. If the transition team is aware of this, it should be able to find ways to improve the new system so it's friendly to business workflows.

The old system may have features which are hard to duplicate. They may not be strictly essential, but people are used to them and like to have them. Sometimes retaining them isn't worth the cost, and employees should learn how to do things differently. Sometimes it's possible to keep those features, or something close, without too much extra effort.

Streamlining the Upgrade Process

An upgrade plan should cover the whole process, from initial planning to the retirement of the legacy system. It needs to be comprehensive yet flexible enough to adjust to unexpected changes. It needs to allow enough time that the inevitable complications don't wreck the schedule. These are the main steps the plan should cover:

  1. Identifying the goals. The reasons for undertaking the project should be clear, and they should be translated into measurable goals.
  2. Talking to the users. The upgrade team needs to know as much as possible about how people currently use the software.
  3. Enumerating the use cases. The team needs a list of all the things the software has to do.
  4. Identifying the steps needed. They will include data conversion and cleanup, creating or acquiring software, and training users. Time estimates are needed for each step.
  5. Defining the transition process. Will there be a sharp cutover from one system to the other, or will the two exist side by side for some time? If it's a cutover, how much downtime will result?
  6. Training the users. They should have experience with a training environment before they start using the new code in production.

Top-quality planning and analysis tools make the process go more smoothly. SMART TS XL helps teams to modernize their software with a minimum of trouble. It covers all phases from initial planning to continuing maintenance. Your team will better be able to understand the requirements of the upgrade, document the required functionality, and bring information together.

With good planning and tools, even a complex legacy upgrade can reach a conclusion that makes all participants happy.

Tags: Legacy Applications, Modernization