Materials requirements planning MRP) is a system that translates a production schedule into requirements for each component needed to meet the schedule. It is usually implemented in the form of a computer-based information system designed to plan and control raw materials used in production. It assumes that forecasted demand is reasonably accurate and that suppliers can deliver based upon this accurate schedule. MRP is a centralized push-through system: output based on forecasted demand is pushed through to the next department or to inventory.

Production flow through a constraint is managed using the drum-buffer-rope (DBR) system. The drum (i.e., the beat to which a production process marches) is the bottleneck operation. The constraint sets the pace for the entire process. The buffer is a minimal amount of work-in-process input to the drum that is maintained to ensure that it is always in operation. The rope is the sequence of activities preceding and including the bottleneck operation that must be coordinated to avoid inventory buildup.

One hundred customers arrive in line per hour and only 60 are serviced per
hour.
Accordingly, the queue will expand to infinity during peaty periods.