How APS Planning Uses Time Fence
The system applies the time fence only during the pull-planning phase of APS Planning. If the system fails to plan the demand using pull planning, and must switch to push planning, it ignores the time fence and uses whatever inventory and supplies are necessary to satisfy the demand as soon as possible.
During the planning process, the system may use or ignore the time fence, depending on the current conditions. The table below shows each of the planning iterations the system may perform and the corresponding treatment of the time fence.
| Planning Pass | |
|---|---|
| A | Pull plan from the demand's Due date and use
Time Fence. If the demand is a pull-up order, pull plan from the Request date.
If pass A is successful, plan the next demand. If pass A fails, perform pass B. |
| B | Pull plan from the demand's Due date and
ignore Time Fence. If the demand is a pull-up order, pull plan from the Request
date.
If pass B is successful, plan the next item. If pass B fails and demand is a pull-up order, perform pass C. If pass B fails and demand is not a pull-up order, perform pass E. |
| C | (Pull-up orders only.) Pull plan from the Due
date and use Time Fence.
If pass C is successful, perform additional pull-planning iterations between the Due date and Request date to try to project a date that is closer to the Request date. If pass C fails, perform pass D |
| D | (Pull-up orders only.) Pull plan from the Due
date and ignore Time Fence.
If pass D is successful, perform additional pull-planning iterations between the Due date and Request date to try to project a date that is closer to the Request date. If pass D fails, perform pass E. |
| E | Push plan from the current date (Time Fence
is ignored during a push).
If pass E is successful (that is, if the system was able to plan a projected completion date within the Plan Horizon, perform pass F. If pass E fails, perform pass G. |
| F | Pull plan again from the projected date
calculated by the push plan and use Time Fence.
If pass F is successful, perform iterative pull-planning using the projected date from the push as the end of the iterations time window. If pass F fails, perform pass G. |
| G | Pull plan from the end of the Plan Horizon
and ignore Time Fence.
If pass G is successful, perform iterative pull-planning using the end of the Plan Horizon as the end of the iterations time window. If pass G fails, mark the item as "Blocked" and begin planning the next item |
| Iterative pull planning | Perform one or more pull-planning iterations within a defined time window,
dividing the window in half with each iteration until a feasible plan is
found that is within the Planning Pull Tolerance or ATP/CTP Pull
Tolerance number of days of the need date. The beginning of the time
window is always the demand's need date (see “ATP/CTP Pull Tolerance
(Days)” and “Planning Pull Tolerance (Days)” for more
information). The end of the time window will be either the projected
completion date from pass E or the end of the Plan Horizon. For example, the first iteration pulls from the midpoint between the projected date and the need date. If that pull succeeds, the next iteration pulls from the midpoint between that new projected date and the need date. The process incrementally moves closer to the need date until it finds a plan that works (that is, doesn't calculate a start date in the past) and has a projected completion date that is within the Pull Tolerance days of the need date. |
Enforcing the Time Fence at the Expense of the Due Date
If you are more concerned with preserving inventory and supply than with meeting the due date, you can disable pass B so APS always uses the Time Fence. To disable this pass, select the Suspend Time Fence (Second Pull) (see “Suspend Time Fence (Second Pull)” for more information) planning parameter. Only manufactured items can suspend the time fence