What Is A Legacy System? Problems And Solutions

What Is A Legacy System? Problems And Solutions

The term “legacy system” is usually used synonymously for heritage systems that ought to get replaced however don’t seem to be, nonetheless, thanks to their core practicality. This text explains the importance of a heritage system, why it exists, its issues, and how it will be replaced.

What is a “Legacy System”?

A “legacy system”,  “old system”, is a previous software system and hardware that’s still in use however has to get replaced. The explanation for a replacement is manifold. What makes the system “legacy” is that it’s thus deeply anchored within the IT infrastructure that it cannot merely be removed or shifted.

The which means of the term is predicated on the terms inheritance, heritage or contaminated website as a trope for the negative presence of the previous system.

Many systems are accustomed to the company’s heart, like our e-commerce software system, client management systems or supply designing, and area units superannuated once a few years of use.

Usually, it’s primarily an issue of quantifiability, property, security and maintenance effort. That is why such a system ought to get replaced.

With the increasing development of technology (see cloud computing, big data, etc.), the question usually arises that systems will grow with it – and that cannot. The latter area unit is referred to as heritage systems, and these area units are sometimes carried on until they get replaced. However, thanks to the deep roots of those core systems

Why do heritage systems exist?

As already printed, heritage systems had their grounds. However, because of the advancement of technology and sometimes exaggerated needs, it is not sensible to develop the system more. However, a transfer is usually difficult for the following reasons:

Integration: heritage systems area unit typically core systems that area unit deeply integrated into the IT design. Commutation these needs careful designing.

Never modification a running system: corporations area units are typically reluctant to switch “functioning” software systems, even though the benefits area unit is clearly outlined. Here, individuals area unit typically the delaying issue, as they’re “used” to operating with such a system.

Monoliths: heritage systems area units typically designed as standalone systems. As a result, the associate degree “all or nothing” replacement method applies rather than revitalizing vital parts, as attainable during a microservices landscape.

Costs: though heritage systems consume tons of resources, the shift and, if necessary, the temporary double operation of 2 systems is far dearer.

Effort: heritage systems area unit typically written in recent programming languages ​​that aren’t any longer used and poorly documented. It’s tough to put in interfaces for brand spanking new systems for migration, and it’s even harder to induce employees with acceptable data. The most useful example is that the European industry that still runs on the superannuated software system.

Legacy system issues:

There is a variety of issues why one would love to switch heritage systems.


One of the biggest issues with a heritage system is that the value of infrastructure and staff. On the one hand, high investment is usually the explanation of why a replacement may be a deterrent. Maintaining the system still causes progress prices.

These prices area unit typically exaggerated by the technology used. Superannuated infrastructure, codebases, and programming languages ​​require specialized spare components and specialist data to ensure the established order. This direct investment is typically conjointly mirrored within the running prices.


The costs for maintenance and therefore the general effort of heritage systems area unit typically above in fashionable design. In extreme cases, there’s no manufacturer support or, with the in-house intoxicant software system, the creators of the systems aren’t any longer in-house.

Tons of your time and energy must be endowed quickly to keep a vital system running rather than worrying about modernizing it.


A particular downside with heritage systems is that the progressively weaker security state of affairs. Whereas current software system vendors offer security updates and endlessly produce bug fixes, nobody is left with heritage systems that offer such basic maintenance.

However the system is employed, this is mirrored during a vital infrastructure liability that should be remedied as quickly as attainable.

ACCESS choices

A few years agone, IT design wasn’t thought of as broadly speaking and holistically these days. As a result, there was seldom a right away application that a system may well be accessed from outside, within or mechanically.

This has been modified in recent years, and therefore the provision of interfaces to alternative systems is progressively turning into a basic capability of the many systems.


In addition to the previous downside, system-internal knowledge management is additionally a challenge. Within the age of AI, knowledge science, and alternative knowledge analytics approaches, it’s vital to extract knowledge from systems as simple as attainable and create it on the market centrally during a knowledge lake.

This can often be not the case with heritage systems, and if so, tough knowledge models or obscure databases tend to thwart the bill.


Not solely the process of knowledge within the sense of insights and innovation is a problem, however conjointly within the GDPR and alternative knowledge protection rules. The concept that knowledge may be known, extracted and deleted simply, quickly and on to go with the info self-determination right isn’t thought-about in several heritage systems.


In addition to inflated prices, integrating a heritage system is one of the most issues. It was not vital to mix systems associate degreed integrate them into an IT design many years agone.

Today, however, this can be the case. And this lack of integration of heritage systems throws all ideas of more development, maintenance and cross-connection through the bill.


The third major downside with heritage systems is measurability. Whereas there’s a wider variety of technologies these days to scale systems or system parts, heritage systems hardly forbade them before the extensive knowledge and IoT era. As a result, most initiatives to bring a heritage system to a modern, interconnected, balanced state can fail.

Approaches to commutation heritage systems

Sooner or later, the replacement of any heritage system must be thought-about. For an imminent replacement, the replacement should be planned when a system choice. Two vital parts have to be compelled to be avoided: failure of practicality and loss of knowledge.


One of the worst cases when replacing an old system is the complete loss of data. Since new data models are rarely designed the same way as old systems, the data transfer must always be carefully planned.

The solution is strategic data migration. For this purpose, the data will be extracted from the legacy system during the replacement and transferred to the new system. More specifically, the following steps should be taken into account:

  • Set up data pipeline for extraction
  • If necessary, clean and filter data.
  • Define and establish data transformations to meet the target data system model (data mapping)
  • Test runs to check the functionality of the data pipeline.
  • Feed all data directly into the new system

During this data migration, particular care must ensure no new data is created or lost. As a result, this migration must occur either parallel with the new system going live or post-doc. Depending on the database, either the data transfer can take place later (e.g. analytics data), or the operation of the system has to be paused (e.g. ERP).


There are essentially three approaches to the direct replacement of the legacy system. Either the system will be replaced directly and irrevocably, and all functionalities will be covered directly by the new system.

Only partial functionalities will gradually be switched live in the new system, or parallel operation will initially occur, allowing both systems’ functionality to be continuously checked.

The most efficient but riskiest way to replace a system is to prepare the new system and then replace the legacy system directly after the data migration.

Subsequently, all operations run directly via the new system, the data is created in the new system, and all users are obliged to work directly with the new software. The disadvantages are obvious:

  • If something does not work, a critical component in the IT infrastructure can be paralyzed.
  • There is a very high need for ad-hoc training.
  • If a replacement fails, data loss is inevitable.


As an alternative, there is the method of successively replacing a legacy system based on functionality. For this purpose, both systems are switched live, and components are only gradually migrated.

This allows a continuous check of the functionality while the effects are kept as low as possible in a failure.

A partial functionality approach increases the security for success and increases the need for care and the organization. This usually increases the project duration massively, as each component is checked before it is considered transferred.

The coordination of the employees must also be precisely controlled to clear which components are to be used in which system.

In this principle, it is sometimes necessary to create interfaces to the legacy system so that (similar to a microservices architecture) the data can be exchanged between the systems. This necessity adds to the effort of preparation.


Another established method in the migration of a legacy system is the temporary full operation of both systems. As you can quickly see, this is the most intensive solution in terms of effort since two full systems have to be maintained and used simultaneously, especially for users who have to record processes in both systems, for example.

However, the advantage is just as obvious: It becomes very clear very quickly whether both systems produce the same results, save the same data and show the same performance. Usually, however, this parallel operation is not maintained for very long because it is very intensive.

Summary: what are legacy systems?

In summary, we hope to have clearly shown why legacy systems exist and what problems they cause. These legacy systems certainly had their right to exist in the past or were or are still absolutely central to the functionality of a company. 

But in the meantime, the technology landscape has evolved, and some systems can no longer keep up with progress. Therefore, it is important to replace such legacy systems – in a structured and planned manner – so that the IT infrastructure does not stand in the way of the entire company’s success.

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