
4 • SCHEDULING FEATURES
27
• • • • •
as shown below. Although this operation time is six hours, this particular process spans a
nine-hour period because it’s paced by the labor availability.
Between 1
PM and 3 PM, there are two units of the resource available. Thus, the operation
is assumed to be at 100% efficiency during that time. However, between 3
PM and 9 PM,
there is only one unit of labor available. The operation will continue during this six-hour
period at 50% efficiency, which accounts for an additional three hours of operation time.
During the last hour of the operation, the efficiency returns to 100% because two labor
units are available.
The spanned operation time can also include periods when there are no units available,
resulting in a zero efficiency during that time. The total number of units requested must be
available when the operation starts. For example, if the operation could not begin until
4
PM of Day 1, the start of the operation would have to be delayed until 9 PM on Day 1 and
would finish at 11
AM on Day 2, as shown below.
7 101 4 7101 4 710
AM PM AM
7 101 4 7101 4 710
AM PM AM
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