Operations Management: An Integrated Approach, 5th Edition

STABILIZING THE MPS

The master scheduler tries to minimize the number of changes made to an authorized MPS because each proposed change can affect the feasibility of the MPS. To deal with MPS changes, companies sometimes use time fence policies. Figure D-2 illustrates the MPS and time fences. The figure shows the demand time fence and the planning time fence, which split the MPS into three parts. The portion of the master schedule from the current time up to the demand time fence is frozen and any changes are kept to a minimum.

Time fence policies

Partition the MPS into areas requiring different operating procedures.

Demand time fence

Establishes that point of time in the future inside of which changes to the MPS must be approved by a higher authority.

Planning time fence

Establishes a point of time in the future inside of which changes must be made by the master scheduler and changes outside of which can be changed by system planning logic.

Companies typically require these changes to be authorized by a person other than the master scheduler because they may need additional resources. This portion of the MPS normally uses all available capacity to produce customer orders. Adding ...