Stability

• Critical legacy systems may well be stable and reliable. Indeed, the better a legacy system works, the more likely key individuals are to refuse to give it up. A legacy system may also feature hardware and software components that are unique and difficult, or impossible, to replace.
  
  

Examples

• Examples of critical legacy systems include process control, test and manufacturing systems. These are typically highly specialized applications built around specific hardware and software products.
  
  

Cost and Legal Implications

• The cost of replacing critical legacy systems is often one reason are maintained rather than replaced. Anyone thinking about replacing a legacy system may also need to contend with regulations regarding the access of data or software certification issues.