Data management refers to several levels of managing data. From bottom to top, they are:
The part of the operating system that manages the physical storage and retrieval of data on a disk or other device. See access method
Software that allows the user to create, store, retrieve and manipulate files interactively. See file management system
The function that manages data as an organizational resource. See data administration
The management of all data/information in an organization. It includes data administration, the standards for defining data and the way in which people perceive and use it.