workstations. The miniload will select the oldest four totes for retrieval, unless the corresponding orders are too young. Each workstation has pipeline capacity, i.e. the maximum number of totes underway to the workstation. This pipeline is used to avoid that a workstation runs idle or its input buffers overflow. If a workstation’s pipeline is full, then a miniload will not retrieve a tote for that workstation. Moreover, part of a workstation’s pipeline is reserved for the oldest order for the workstation. Totes for younger customer orders will not be selected for retrieval if the non-reserved pipeline is full. This means that a miniload may retrieve fewer than four totes per retrieval cycle.