The benefits of using this technology are so abundant to make one wonder how come everyone is not using it.

Should we take a look at the conditions an organization or company has to meet to be able to use a MRP/CRP system, an answer would offer itself.

Below you can observe what are the conditions to be met for MRP/CRP system eligibility:
1. Effective and high-performance computer system
2. Precise computer controlled tracking of stock and requirements for all items used by the orgranization
3. Manufacturing, where discrete products are manufactured through major production processes from raw materials, components or semi-finished products
4. Manufacturing, which requires longer production
5. Reliability in identification of time required for specific tasks
6. Main production plan can be put on hold until raw materials are supplied and planning is peformed without exceeding costs or setbacks
7. Support and decision-making of management

Of course, an effective high-end computer system is an absolute prerequisite. The other two characteristics, which almost need not be mentioned, are precise quantity of stock and material requirements on the other hand. Still these two things are most cumbersome hindering MRP system implementation. Time it would take for implementing the system can turn into time spent in removing errors.

Usually, a MRP system is used solely in manufacturing. The organizations manufacture discrete products using specifications. That is, MRP is rarely used in service industry, trade, transport companies and other non-manufacturing organizations.

Implementing MRP is most useful for process-oriendted systems, and there where process times are longer and involve more complex multi-level steps in production. Planning stock and production in such systems is a most painstaking process. Let us take a look at a hypothetical manufacturing system where raw materials are used in production of products. Here raw materials are ordered precisely following material requirements for finished products. Complex monitoring of manufacturing is not required here. Yet in most production systems you have take into account time required for ordering raw materials, time between individual stages and last but not least time spent in processing them. Using MRP system you can delay time planned for supplying orders, thus making monitoring of manufacturing processes easier and optimizing stock quantity.

To make your MRP system efficient you need to identify required time. Furthermore, you have to put the main production plan on hold prior to actually starting production. This means that you know with certainty the temporal and quantity framework needed to produce what you want. You also have to know temporal and quantity aspect of raw materials required in production.

MPR system is not implemented (and most probably will not be) in all manufacturing systems. MPR is redundant or economically unjustified in simple manufacturing. Yet use of MRP systems is growing exceedingly due to savings it brings.

But from the usage we can see that the MRP system is not the be-all end-all bringing answers to all our questions. First of all it does not save you against all the troubles in planning stock and capacities. After all MRP is nothing more than a computer-controlled system for monitoring manufacturing. As any other computer system it can only be as good and sound as are information fed into it. Incorrect quantity of stock or material requirements generates an incorrect main production plan. And should we add a probable faulty managing of organization, we get multiple incorrect or misfed information.

MPR can best be used in well-managed manufacturing systems. The only thing an organization would need is a high-performance system for monitoring and planning.

Implementing MRP system can be a painstaking process. Just purchasing high-end software and hardware is far from enough. You have to keep in mind substantial start-up costs as well as fixed maintenance and operating costs. A major part of costs is incurred in ensuring and repairing bad or non-existing data. Plus, costs are incurred when ensuring discipline required in order to provide data flow to MRP system. Usually, it handles of implicit costs which cannot be included in the offer for computer-controlled manufacturing.

From "Production and Operations Management" by Normana Gaitherja and Grega Fraizerja