Within any project organisation, inflight projects can be interrupted (preemption/shutdown) for any number of reasons. Part 1-of-2.
Preemption occurs when an inflight project is told to prematurely end one or more deliverables and then goes on-hold for a fixed period of time. Once preempted, deliverables can be finished by another project, finished later by the project else never finished at all. Preemption options include,
- Deliverable closest to finishing.
- All deliverables being processed.
- Deliverable with the lowest priority.
- Deliverable furthest from finishing.
- Only deliverables with a particular attribute.
Project Preemption Model
A queuing system can be modelled in such a way that inflight projects with a low priority can be preempted to make room for a higher priority project as they arrive in the queue. In the model below, the queue reports the project priority while the Service reports the lowest priority project. Project priority information is sent to the decision block. If it is determined there is a higher priority project in the queue, a signal is sent to the Service informing it to stop and store the remaining project time. When the preempted project returns to be delivered, it will be serviced only for the time remaining.
Project Preemption Summary
In project organisations, it is common for preemption to occur. This can be for any reason such as the arrival of a project that has a higher delivery priority, random system failures, planned maintenance, the occurrence of a higher priority event etc. The challenge of project preemption is that it always comes with a cost – not shown in the model. Not only is there the decision of how best to finish the deliverable and start the higher priority project – immediately and discard all the work to date else take up valuable time and complete the deliverable, on resumption a setup time and associated cost is needed to allow the project team to get back up to speed and/or setup the deliverable environment along with the challenge of rescheduling the on-hold project with other inflight and pipeline projects.
Organisations experiencing continued project preemption indicates there is a likely systemic upstream planning and/or downstream delivery failure the root cause of which needs to be investigated and resolved.
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