What are the Basic Rules for Autoschedule in PPM and OWB?

Document ID : KB000051700
Last Modified Date : 11/04/2018
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Question:

When using Autoschedule in CA PPM's Gantt and OWB in what order are tasks scheduled?

Answer:

First, Autoschedule schedules work that has no flexibility

  • actual work
  • fixed assignments
  • all work on locked tasks

and reduces the remaining availability accordingly.

Next, Autoschedule processes the remaining tasks in order of a calculated priority (see below) subject to task dependencies. As each task is processed, remaining availability is reduced accordingly.

The calculated priority is based on the following factors, considered in this order.

  1. If the task has a Must Start On or Must Finish On date constraint
  2. Task Priority (lower values rank higher)
  3. Task Float (lower values rank higher)
  4. If the task is started
  5. WBS order (i.e., the physical location that it is seen in a view; tasks towards the top rank higher)

If a task "ties" with another task, the next factor is taken into account. Thus, for example, a task with no date constraint and a priority of 5 will be scheduled before another task that also has no date constraint and a priority of 5 if the first task's float is less than the second task's.

Autoschedule gives priority to constrained tasks over non-constrained task, and to inflexible constraints (such as "Must Start On") over flexible constraints (such as "Start No Later Than"). Constraints are overridden when it would violate a dependency or over allocate resources.

Additional Information:
Reference KB000008847 - When Autoscheduling in the PPM Gant or Open Workbench (OWB), all ETC is getting scheduled for one day for some assignments
Reference KB000029379  - OWB Autoschedule does not schedule correctly when Max % Load is set to 100% and Resource Constraints is Checked
Reference KB000077074 - Autoscheduling is Changing the Task Date even though there are no Dependencies or Assignments
Reference KB000046114 - How do Resource's Allocation dates impact Autoscheduling in the Gantt for tasks with assignments? 
Reference Automatically Create Project Schedules with Autoschedule for more information on Autoscheduling including how to lock tasks