What is the purpose of the "aggregator" ?
The METADATA Creation tool will assign a sequential number as an aggregator. The aggregator name (number) is used as a secondary directory name to limit the number of objects that are stored in the directory structure.
This directory sits under the top level Institutional directory and above the root identifier named directory which holds or contains the digital objects. It is useful to limit the overburdening of most modern operating system from having too many items in a single directory.