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WHEEL OF MISFORTUNE 141

I have been researching this subject for quite some time, and the more in-
volved in it I get the more I find it Byzantine and intriguing. It is a fairly complex
topic. There is probably more information here than you need to know. We start
by looking at some of the issues and problems involving resource leveling. Then,
we study the resource leveling process, itself, and examine the results of 13 prod-
ucts on some test projects. Next, we look at the resource scheduling attributes
and calculations of these products. We also look at some alternate software for re-
source management. Finally, in Chapter 4.4, we explore the Practical Uses of Re-
source Scheduling.

Wheel of Misfortune: The Resource Leveling Process

Resource leveling is certainly not new, and neither are the issues pertaining to the
best and practical methods to be used. I was recently browsing through a 1981
P/2 manual (PROJECT/2 from Project Software & Development, Inc.). P/2, then
running on IBM mainframes and the DEC VAX, offered powerful resource
scheduling options. The user had the choice of four leveling methods, two paral-
lel and two serial modes.

The parallel mode, which is seldom used today, will usually (but not always)
produce a shorter-duration, resource-constrained schedule. The parallel method
looks at the project by time periods. For each time period, it looks at all the tasks
that are scheduled to be worked and assigns resources according to the user pre-
ferred ranking criteria. Activities that cannot be scheduled in that time period,
due to insufficient resources, are postponed until a later time period. Then the
system moves to the next time period and reconsiders the next set of tasks that are
ready to be worked.

The serial mode considers the project on an activity by activity basis, and gen-
erally takes less time to process. For any particular time period, it starts out as
above. However, when it cannot schedule an activity on its earliest start period, it
looks for the first available period (resource availability) and immediately sched-
ules that activity at that future time. It is possible, therefore, that when the system
gets to a later time period, one or more tasks may already be scheduled, before
checking for the best choice or closest support of the ranking criteria. We will find
that the serial method of resource leveling is almost universally employed in to-
day’s popular products.

With either method, the user is often allowed to identify a set of ranking fac-
tors (sometimes called ordering, prioritization, or heuristics). These are condi-
tions that will influence the selection of tasks where some tasks must be delayed.
Common factors are date values (ES, EF, LS, LF), float values, task duration, as-
signed priorities, task IDs, and user sort sequences. During resource leveling, the