Provided are a computer program product, system, and method for determining tracks to release in a target volume mirroring tracks from a source volume. Tracks received from the source volume are written to the target volume to form a consistency group of tracks in the source volume at the target volume. A determination is made of tracks available to release from a volume table providing a state of the tracks in the target volume and space allocated to the determined tracks is released. A point-in-time copy of the target volume is crated and complete is returned to forming the consistency group in response to releasing the space and creating the point-in-time copy.