A computer-implemented method and a computer processing system are provided for increasing memory density in a memory using heap contraction. The method includes dividing the heap into a plurality of work regions including a last region and other regions such the last region is larger in size than the other regions. The method further includes calculating a size of the heap contraction. The method also includes forming a pair of the last region and one of the other regions that has a largest free portion. The method additionally includes executing intra-table compaction and inter-table compaction on the heap. The method further includes contracting the last region by subtracting a prescribed space from the last region.