Learn in the textbookPromoting and Evaluating System Utilization
DefinitionDisposal and renewal of legacy systems (レガシーシステムの廃棄・刷新) means retiring an existing system that has long run on old technology, or rebuilding it as a new one.
ExplanationA legacy system (レガシーシステム) is an existing system whose internals have grown complex through years of modifications, with fewer and fewer people able to handle its old technology, so maintaining it takes much effort and money. The longer it stays in use, the more its maintenance costs pile up and the slower it adapts to new business needs, so disposal or renewal is decided in a planned way.
AnalogyIt resembles deciding whether to keep repairing an old machine whose parts are no longer made or to replace it, by weighing the cost and effort involved.
Memory hookLegacy means inheritance. Think of property handed down to you that becomes a burden if kept as it is.