A method for allocating new data sets while taking into account point-in-time copy relationships is disclosed. In one embodiment, such a method includes determining free space that is available in a volume. The method further determines which portions of the free space are not subject to residual point-in-time-copy relationships. In certain embodiments, these portions are represented in a modified free space mapping that identifies storage elements (e.g., tracks. groups of tracks, etc.) in the volume that make up the free space but are not subject to residual point-in-time-copy relationships. Once the portions are known, the method determines whether the portions are sufficient to accommodate the allocation of a new data set. If the portions are sufficient, the method allocates the new data set therein. A corresponding system and computer program product are also disclosed.