Backlog and Reserves

Backlog noun - An accumulation of jobs not done or materials not processed that are yet to be dealt with (especially unfilled customer orders for products or services).

Reserves is a synonym for backlog in stockpile topic. In some cases you can use "Reserves" instead a noun "Backlog".

Reserves noun - Civilians trained as soldiers but not part of the regular army.

Backlog is a synonym for reserves in supply topic. You can use "Backlog" instead a noun "Reserves", if it concerns topics such as stockpile.