What is Legacy System ?
Legacy systems utilize programming languages, software and/or hardware that typically are no longer sold by their respective vendors, in some cases they are no longer supported
by the original vendors.
Because re-designing already well running systems and organizational structures by whole project teams is frequently uneconomical and may be detrimental to focusing on new business demands. Typically viewed by non-technical executives as tried and true technology, they are often upgraded at various points, and they have the power of inertia behind them.
These systems are often mission critical with redundancy and security built into them. Many eyes they see them as tried and tested without immediate comparative replacement options or the options are very limited and/or beyond the budget.
The limitation of the lifecycle from the OEM, reflecting ‘End of Life’ availability from distribution channels does not reflect the economic and business usefulness of the system.
Most leading global enterprises are reliant on decades-old legacy systems. IT research shows that 90% of the companies continue to use EOL hardware 3-5 years after the manufacturer stops production of the original models. In fact, this uptake of adding to legacy platforms and providing the disaster recovery and spares replacements for support of legacy systems is viewed by the manufacturers as a major source of revenue and has seen the invent of OEMs remanufacturing their own legacy systems as well as spare parts.
Initiating new platforms, especially when original source code is not available involves extensive programming and the potential risk of business interruption associated with the movement of data and key business processes to more advanced and contemporary technologies is deemed too risky. In the utility market as well as defense and finance there are prescriptive legislative impediments to migration which require extensive testing of newer technology, which itself is often legacy by the time it comes online.
Re-deployment of once used systems avoids scraping of systems that may be upgraded and saves them from landfill. Each new system has associated environmental costs of mining minerals, producing plastics and metals, and freight which is extensive in the age of build to order models in a global factory network.