X TZ i X jiz i X Ytz J

FIGURE 22-9. Effect of bad multitasking.

on for a few hours or days, and then the work is stopped. The resource works for a period of time on task Y, and then on task Z. This rotation of work continues until each task is complete.

There is an obvious impact on the time that it now takes to complete each task. Even if this resource, by magic, could start each task without any start-up time, the first task would not finish until mid-April. The cycle time of that task is no longer three weeks—it is now seven weeks, or more, because people cannot start immediately where they left off. With some types of work, such as computer programming or engineering design, the impact of start-up time can be severe.

However, there is sometimes a more devastating effect in terms of quality, and that is rework. Bad multitasking may impinge so heavily on concentration that people start making mistakes. The implication in Figure 22-9 is that nine weeks of total work will actually take twelve to fifteen weeks in a multitasking environment.

Simulation exercises show that the effect of bad multitasking is to increase project cycle times by more than 100 percent. In the Critical Chain case studies, the effects were even worse.

In the multiproject environment, the system's constraint can be stated as the management practice of pushing work into the system irrespective of the capacity of the resources to perform the work. The system's arteries are clogged.

Dr. Goldratt states "The more complex the problem, the simpler the solution must be, or it will not work." It would be far too complex, and probably futile, to try to schedule all of an organization's resources across projects and other work. However, a simple solution is to schedule multiple projects according to one resource—the most heavily loaded resource across all projects. This resource is the one most likely to impact the cycle time of the entire collection of an organization's projects.

In Critical Chain, this resource is called the "drum." The analogy is soldiers marching in battle. In order to keep the soldiers together, marching at the same pace, a soldier beats a drum to set the pace. In Critical Chain, the capacity of the organization's critical resource sets the pace of all projects. That resource beats the drum.

Project start dates are staggered according to the capacity of the drum resource. The top management of the company reaches consensus on the organization's drum and sub sequently, the priority (i.e., which project is staggered first, second, third, etc.). If some projects do not use the drum resource at all, those projects can be scheduled at any time.

Usually, when senior managers are educated on Critical Chain, they are able to identify a few candidates for a drum resource. Sometimes, it is not obvious which candidate is the best choice. In this case, the process can be facilitated by doing Critical Chain project plans for some or all active projects, loading the information into a Critical Chain software package, and looking at the resulting reports on resource loading.

One important piece of information is the percentage of projects that the different resources are utilized on. The other piece of information is the percentage utilization of each resource. In combination, these data help identify the drum resource.

To begin staggering projects according to the capacity of the drum resource, some current projects must be deactivated or the drum resource must be given additional capacity. Typically, many projects are deactivated.

A significant example comes from an aircraft maintenance group. A country was given several defense aircraft as a gift. The aircraft were overdue for their major maintenance cycle. Each aircraft had dozens of problems that required the expertise of a small group of highly trained engineers. On average, each problem required 135 days to resolve. Over a period of several years, the maintenance function had been unsuccessful in getting a single aircraft back into operation.

The expert engineers were allowed to work unlimited overtime, but this did not change the results. On average, each engineer had several dozen problems he was working on.

Upon implementation of Critical Chain, each engineer was limited to a maximum of three open problems. Considering each problem as a project, several dozen projects per engineer were deactivated.

The results were published. Over a five-month period, the average lead time per problem (from the time the problem was identified until complete) went from 135 days to fewer than 30 days. Overtime declined to almost zero.

In most cases, the resource that appears to be the most heavily loaded across projects in fact has huge excess capacity. The excess capacity is masked by bad multitasking caused by too many concurrently active projects in the system. Once the projects are staggered, the organization is able to flow many more projects through the same resource pool.

In combination with implementing buffers and buffer management, the staggering of projects provides predictability in the project management environment. Managers are able to separate planning from execution without having to replan projects whenever Murphy's law hits.

To further insulate projects from each other, implementers use a buffer called the strategic resource buffer. This buffer simply puts gaps between the date that the strategic resource is due to be released from one project and their scheduled start date on the next project. In this way, if the strategic resource is late finishing one project, it has no or little impact on the schedules of all following projects. The rule of thumb for the size of this buffer is 30-50 percent of the size (in days) of the tasks that the strategic resource is performing.

One other buffer is designed to protect the critical resource from wasting its time. When the critical resource arrives on a project, the organization wants to ensure that the work is there waiting for them and not vice versa. Therefore, any tasks that feed work to the drum resource are scheduled to be completed ahead of when the work is needed.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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