What Is the Capacity Search Window in Scheduling?

The capacity search window is the maximum number of days forward the scheduling engine may walk while looking for free capacity to place an operation. It starts at the operation's earliest legal start and checks each day's shifts in turn until it either finds room or runs out of window. EDGEBIC by User Solutions sets a generous default because the window exists to stop an impossible search, not to constrain a legitimate one.

How it works

Placing an operation is a search. The engine knows the earliest moment the operation could start, taking predecessors, queue time, transit, and any pins into account. From there it walks forward: does this work center have a shift running on this date, does that shift have capacity left after everything already booked, is there an instance free, and is the remaining capacity enough to be worth allocating? If yes, the operation is placed, possibly split across several shifts and days. If no, the engine moves to the next day and asks again.

That walk needs an end. In a healthy plant it ends quickly, because the machine has hours and the queue is finite. But some situations have no natural end at all. A work center with no shift assigned has zero hours on every day forever. A capacity override of zero left in place across an open-ended range produces the same result. A utilization percentage set so low that every cell rounds to nothing does too. In each case the engine can walk for years of simulated calendar and find exactly the same empty answer each time.

The search window converts that into a bounded outcome. When the walk exceeds the configured number of days, the engine stops and reports that the operation could not be placed, which surfaces to the planner as a scheduling problem rather than as a run that never completes.

The size of the default matters. It is set high, in the thousands of days, precisely because a long queue is not an error. A constraint machine booked many months out is a real and common situation, and the honest scheduling answer is a far-out date, not a refusal. Tightening the window to catch problems faster tends to convert legitimate congestion into false failures, which is a worse outcome than the slow search it was meant to prevent.

The correct diagnostic reflex, therefore, is that hitting the window is almost always a capacity configuration signal rather than a window sizing signal.

A concrete example

Imagine ringing round to book a table. You start with tonight, then tomorrow, then the night after, working forward until somewhere has space. If the restaurant is popular you might get to next Friday before you find room, and that is a real answer, just not the one you wanted.

Now imagine the restaurant has permanently closed and nobody told you. You could work forward through the calendar for the rest of your life and never find a table, because there is no table to find. At some point you have to decide to stop calling and conclude that something is wrong with your assumption rather than with the dates.

The search window is that decision to stop calling, made in advance. Set it at a few days and you will give up on a popular restaurant that genuinely has space next Friday. Set it at a couple of years and you will find any real booking that exists while still eventually noticing that a closed restaurant is closed.

In a plant: a mill with two shifts and six weeks of backlog is the popular restaurant. A mill with no shift assigned to it at all is the closed one, and the window is what turns that from a hang into a message.

How EDGEBIC uses it

The window is a scheduling policy setting, adjusted alongside the rest of the engine's behavior rather than per job, and changing it is covered in how to set the capacity search window. The settings record it belongs to is the glossary term scheduling policy.

Because hitting the window is usually a capacity problem, the useful companions are the capacity terms. What the engine is actually looking for each day is available capacity, how that number is produced for a given cell is walked through in how EDGEBIC resolves capacity day by day, and the order in which shifts are tried during the walk is explained in how shift priority scoring orders the capacity search.

The capacity search window is a leash on an impossible question, not a limit on an honest answer. For the wider vocabulary, see the manufacturing glossary, and to see capacity searched against a live plan, explore EDGEBIC.