repition of data

when data is duplicated in a system' it is much more difficult to maintain the integrity of that data. When the data is changed in one location' it must also be changed everywhere that the data exists. In a decentralized environment, this can be difficult at best. If ultimately unusable. also, because the data exists in several locations, the data must be entered more than once. this is time-consuming and wasteful. And because the data is duplicated, it requires more storage space to maintain it.