Sustainment involves the supportability of fielded (marketed) systems and their subsequent life cycle product support, from initial procurement to supply chain management (including maintenance) to reutilization and disposal. It includes sustainment functions such as initial provisioning, cataloging, inventory management and warehousing, and depot and field level maintenance. Sustainment begins when any portion of the production quantity has been fielded for operational use. Sustainment includes assessment, execution and oversight of performance based logistics initiatives. In short, sustainment logistics includes anything required to maintain, sustain and repair the item and keep it in operational order.