1. In a data processing system storing a plurality of discrete entities, each identified by a single parameter within a monotonic parameter spectrum, each resident at an addressable location and each locatable by searching a system maintained addresses, a method of maintaining said multi-level index by said system comprising the steps of: executing a sequence of processing cycles wherein each cycle progresses through the index levels in a first and then a second direction, selectively performing at each level of the index, while performing a processing cycle in said first direction, a first subset of basic operation iterations, including, basic operations for duplicating the presence of an original parameter, and selectively performing at each level of the index, while performing a processing cycle in said second direction, a second subset of basic operation iterations including, basic operations for deleting the original presence of said duplicated parameter.