Project Sequencing Big Rocks First

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The next step is to determine how the projects can be pipelined through your project delivery system. A given mix of projects may cause a resource to constrain the availability of your system to de liver the projects you have selected, at least adjusting the time you should plan on starting the projects. As illustrated above for multi-project TOC project management, you need to sequence the projects anyway to keep the individual project durations as short as possible. The TOC approach to sequencing projects is called pipelining. It creates a schedule for the drum resource (that resource which sets the beat for the whole project system) for all of the projects and then translates that back to schedules for each individual project. The master scheduler levels the work for only the drum resource across all of the projects. The work for other resources is not leveled across all projects.

There is an urban legend about a science professor who provided a demonstration to his class. He put a very large glass jar on the lab bench and put some large rocks into it. He asked the students, "Is it full?" They answered, "Yes." He then picked up a can filled with small pebbles and poured them in around the big rocks. He asked again, "Is it full?" The students, getting the idea, smiled and said, "Yes, now it's full." He then picked up a can with sand in it, and poured the sand in around the pebbles, and asked again, "Is it full?" The students, now a little worried, tentatively answered yes again. Finally, in the version I like best, he picked up a large bottle of beer and poured it into the jar, telling the students, "Now it is full. The purpose of this demonstration is to show that there is always room for beer." No, the purpose was to show that what at first appears to be a full system may not be full. The same will be true for your project delivery system as you add projects to it. You can often add more projects that do not use much of the drum resource without affecting all of the other projects.

As noted earlier, all projects are not created equally (see Table 8.1-1). Projects that you have committed to clients are, by and large, more important than internal improvement projects. Yet both types of projects may compete for the same resources within your company. One way of reconciling the priority conflict is to use the matrix presented in Table 8.1-1 for types of projects to guide placing projects in the drum schedule. First overall priority should go to projects that you have company commitments for (see Table 8.1-4).

Table 8.1-4 An Approach to Entering Projects into the Drum Schedule

Date Driven



Priority I:

Priority II:

Big rocks: first access


to drum



Priority III: As necessary

Priority IV:

Throughput/constraint sequence

You can fit the other projects in around them. There may also be some relatively high-priority projects that you have to do (for example, regulatory requirement, broken infrastructure, obsolete software) but don't have an identifiable ROI. Those should be priority 3 initially, but may move up to priority 2 if they can't meet need dates as priority 3.

You should then use your risk-adjusted ranking to put the projects into the drum schedule. You can use the risk-adjusted ROI as demonstrated to select the projects, or you can rerank the projects you have selected in terms of the amount of throughput (T) they will use relative to the amount of the drum resource (constraint, C) they demand, that is, the T/C ratio.

Figure 8.1-11 illustrates a TOC scheduling tool used to perform project pipelining. The Concerto software uses Microsoft Project to plan each individual project as a critical chain project and then provides an easy to use tool to insert projects into the multiproject schedule and estimate the impact on all of the projects in the system.

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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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