Theory of Constraints Handbook - James Cox Iii [754]
9The TOCICO Dictionary (Sullivan, et. al., 2007, 41) defines “resource buffer—A warning mechanism used in single project environments to ensure that resources working on a Critical Chain task are available when needed.” (© TOCICO 2007, used by permission all rights reserved.)
10In terms of the TOC five-step process, acquiring additional resources (Step 7) corresponds to Step 4, “elevate.”
11This method is a good rule of thumb or heuristic technique, when scheduling manually, but does not always identify the best Critical Chain.
12Because Resource 4 will proceed to Task F as soon as Task H is completed (following standard CC procedure), there is no need to be overly concerned with timely completion of the top path.
13Infrequently, a gap may occur on the Critical Chain due to the insertion of a feeding buffer that requires additional resource leveling. These gaps generally are ignored.
14In this simple example, both Task C and Task I are predecessors to Task J, so the choice of which one on which to focus is debatable. Thus, the situation described here is not typical and Resource 3 may elect to continue working on Task I until it is completed.
15CC Step 6 corresponds to Step 3, “subordinate,” in the TOC 5-step process.
16In place of resource buffers, some organizations simply report upcoming CC tasks and path starts.
17CC software will find the best (shortest) schedule, but if scheduling is performed manually, a schedule that “works” is good enough.
18As noted in footnote 14, both Task I and Task C must be completed prior to the start of Task J and therefore a late completion on Task I might not trigger a move to Task C until Task I is finished.
19See Guideline XII in Chapter 2.
20This terminology is used in the TOCICO Dictionary and includes a reference to “drum resource” (Sullivan et al., 2007, 7).
21In the software industry, integration occurs where various new systems are aggregated and merged together or into older programs.
22Note that there may be multiple SRs, reducing required buffer sizes to decouple projects.
23Buffer recoveries occur in a similar manner when actual task duration requires less than its estimated (aggressive) duration.
24With available software, “fever charts” (Newbold, 2008, 112) track buffer consumption and automatically resize buffers throughout the life of a project. An example of such a chart is shown later in Fig. 3-11.
25For example, homes and businesses located outside of designated flood plains in Atlanta, GA suffered severe flooding in September 2009.
26There are few instances of budget amounts, once assigned, being returned to the organization.
27This general statement is not true for cost-plus contracts. With cost-plus contracts, the value of the project is actual costs incurred plus some margin, such as 20 percent of total costs. These contracts are becoming quite rare and typically involve research and development type projects where the project deliverable is so unique it is impossible to estimate the total cost to complete the project and achieve its objectives.
28Because estimation of both overhead costs and driver quantities is imperfect, the allocation rate used during a year (or whatever time until the rate is recomputed) most likely will be adjusted once actual costs and actual driver quantities are known. That means that overhead costs allocated to projects may be adjusted later, sometimes after a project has been completed.
29If there is uncertainty concerning the actual cost of materials, some amounts representing material cost variability may be added to a project’s budget buffer, an account established for task duration variability.
30A budget buffer represents the budget associated with the safety time removed from individual tasks. The budget associated with the time placed in the project buffer is under the control of the PM while the budget amount associated with the time removed from individual tasks and not connected with the time placed