Why is APS necessary?
The shortest answer is: to extend the functionality of ERP system, particularly in the field of planning and scheduling.
ERP systems are:
- Large - because they bring many functionalities to large number of users in the company
- Strong - because they enable integration of large quantaties of the most various data
- Inert - because of the integration of many functionalities each change requires a careful analysis of the impact of these changes on the system as a whole
In terms of planning, typical ERP system usually has at least one of the following restrictions:
- Planning assumes unrestricted resurces
- Planning is done in same time units (day, week, month)
- Planning is based on a backward scheduling of operations
- It assumes the average preparation time for operations, regardless of the planned schedule
- Planning relies on many other assumptions and simplifications, primarly due to the lack of detailed data on resurces and rights that effect operations flow
Quality ERP system will enable development of a precise and workable plan at a higher level (aggregate plans and short-term detailed plans), but will not be able to make a quality operating plan or schedule. Even those ERP systems that within its functionalities provide the user with a scheduling tool, in the best case would suggest a good operating schedule, but will not sufficiently help in the case of a change. Reaction to changes in the operation or in an unplanned event, is a challenge that ERP either cannot or should overcome. ERP systems are essentially transactional systems, per its technology, but also per its conception. APS system requires fast algorithms that perform mathematical calculations directly into the computer's memory and by that are substantially different from the ERP system.
APS system is not necessary because the ERP system "is not good enough". Nobody would expect from an ERP system to solve tasks for which are used CAD systems or other software products. As same as CAD is specialist for technical drawing and documentation, APS system is a specialist for planning and scheduling.
Wise ERP system will gladly give over part of work from the APS domain to - APS system...