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It is important to understand that when a location or resource goes off shift, it is essentially down. We call this type of downtime a shift downtime and it is treated slightly differently from other downtimes. Breaks, which are also part of the shift schedule, are treated exactly like clock-based downtimes. These downtimes are discussed in Locations and Resources.
All location shift downtimes have a default priority of 99, the highest non-preemptive priority possible. This means that when a location is scheduled to go off-shift, this downtime will take priority over all other entities with a priority less than 99 waiting for the location. If the location is currently in use, shift downtimes allow the current entity to complete its process at the location. After the entity is finished, the shift downtime proceeds as if it started at its scheduled time. This means that the location becomes available at the start of the next shift regardless of when it actually went off shift. This procedure is demonstrated in the following example.
Although the downtime is scheduled to last from time T2 to T4, the actual downtime does not begin until time T3. This is what happens for both locations and resources currently busy when the shift downtime is scheduled to occur.
To preempt a location in which an entity is currently processing, set the priority for going off shift to a number one level higher than the entity’s priority.
Please note
Since the entity was preempted, the remaining time for the entity to be processed at the location was completed after the location shift downtime was completed.
An off-shift location may be preempted back into service by an entity. Following the preemption, the shift downtime will resume for any remaining time before the start of the next shift. The following example demonstrates this principle.
In this example an entity with priority of 200 or greater preempts an off-shift location. The location becomes available to process the entity. Once processing is complete, the location returns to its off-shift status.
In order for an entity to preempt any location downtime (shift or otherwise), it must have a priority level that is at least 2 levels higher than the downtime's priority. In this example the location shift downtime has a priority level of 99 so the entity must have a priority level of 200 or greater to preempt the shift.
If a preemptive clock downtime occurs during a shift downtime, the downtimes simply overlap.
This example shows the effect of a preemptive downtime occurring for a location already off-shift due to a shift downtime. Because location downtimes always overlap, the effect is as if the preemptive downtime never occurred. The location remains off-shift for the total duration of the shift downtime.
The example above could represent the situation where a recurring downtime, such as a lunch or dinner break, has been defined for a single location that is scheduled to be available for a two-shift period. It would be simpler to specify a single downtime for lunch and dinner that occurs once every 8 hours continuously than to define separate downtimes for lunch and dinner. In this case the preempting downtime would represent a meal break occurring while the location was off-shift.