A mechanism is provided for destaging one or more data files in a volatile memory using a set of heat registers associated with each data file. Responsive to receiving a notification indicating that free space within the volatile memory has fallen below a predetermined threshold, a rule is implemented, based on values associated with the set of heat registers assigned to each data file, to identify a data file to move to a non-volatile memory, where the set of heat registers comprises a content heat register, an access heat register, and a metadata heat register. The data file is moved to the nonvolatile memory. Responsive to determining that the free space fails to have risen above the predetermined threshold, the operations are repeated until the free space rises above the predetermined threshold at which time the set of heat registers assigned to the data files that were moved are deassigned.