Computer applications, both hardware and software, which have been inherited through previous acquisition and installation. Most often, these systems run business applications that are not integrated with each other. Newer systems which stress open design and distributed processing capacity are gradually replacing such systems.
Hardware and software applications in which a company has already invested considerable time and money. Legacy systems typically perform critical operations in companies for many years even though they may no longer use state-of-the-art technology. Replacing legacy systems can be disruptive and therefore requires careful planning and appropriate migration support from the manufacturer.
Existing applications and repositories of data; often large and containing years' worth of information. Can be mainframe, midrange, or network based.