With auto scheduling, Celoxis computes the start and end dates for each task taking into consideration the work/effort, allocation, duration, resources work-timing, vacations etc...
The essence of automatic scheduling is governed by a simple formula:
Effort = Duration * Resource Units OR W = D * U
Before, we understand the equation, let us understand the variables involved:
Work or Effort:
Work is the amount of effort ( independent of a resource) required to complete the task. Typically it is described in man-hours. Effort indicated is irrespective of holidays and resources since not all resources may be working equal hours.
Duration:
Duration is the length of working time between the start and finish of a task. The working time for a task is defined by the project and resource calendars. For example, If today is Monday and you say "I want this report by Friday" you are indicating a duration. It does not mean that the resource must spend all their time to prepare the report. The actual report preparation may take only 5 hours. In this case 5 hours is the effort but the duration is 5 days assuming that there are no holidays in between.
Units:
Resource units indicate how much of a resource's available time, according to their work calendar, is being used to work on a particular task. Allocation is a way to have a resource work on multiple activities at the same time. It can be specified as a percentage of daily working time or as a total number of hours that a resource must spend on the task.
For example, if a resource works 8 hour every day and you allocate that resource for 50% on a task, you are effectively saying - spend 4 hours on that task daily. On the other hand if you enter allocation in hours it indicates that the resource should work a total of those hours on a task.
Let's see some examples so see how it works. For all these examples, assume that the 1 Man-day = 8 hours and all resources also work 8 hours per day.
A task requires 16 hours effort to finish and you assign a resource to work full time (i.e 8 hours per day). How long would it take to complete the task? If you said 2 days, you are right. Let's see if the equation matches with our expectation. In this case, effort = 16 hours and resource allocation is 1 (i.e 100%). So duration = 16 ÷ 1 = 16 hours or 2 days since each day is 8 hours.
Now assume that you add one more resource to the task. How long would it take to finish the task? Again, it's quite easy - 1 day. Both resources will work 8 hours each and finish the 16 hour task in a day. Let's see again if the equation matches with our expectation. In this case, effort remains 16 hours while allocation is 1 + 1 = 2. So duration = 16 ÷ 2 = 8 hours or 1 day. Now let's make it a bit harder. If both resources are told to work only 2 hours per day i.e 25%, then how long would it take? Effort remains 16 hours while allocation is now 0.25 + 0.25 = 0.5. So duration = 16 ÷ 0.5 = 32 hours i.e. 4 working days.
To get the most out of scheduling, you need to understand and effectively use all three parts of the scheduling formula: W = D * U. You can control which of the scheduling formula parameter has the most influence over the task's scheduling.
There are many other factors that Celoxis takes into consideration while scheduling a task. Let us look at them.