 Systems can run indefinitely without gradual space leaks or long interruptions during garbage reclamation phases.When a data structure becomes empty, all of its space is recycled, rather than leaving behind 'tombstones' or other place holders.For example, a possibly very large multi-value attribute may shrink to one value, becoming as efficient as any single-valued attribute, and if that last value is deleted, all space for it is reclaimed, including the space for the attribute it was attached to, and if a row has only attributes with no values, the row is reclaimed completely as well.