To see this in action, try creating a circular dependency in which two tasks both depend on each other. Because this is logically impossible, a violation will occur.

This window lists all of the violations in the project, along with explanations of why they have occurred. Most violation explanations include links you can click to immediately resolve the problem.

If the automated resolution provided by the Violations Window isn’t what you want, tips at the bottom of the window will help determine the source of the problem so you can fix it based on your scheduling needs.

By default and prior to leveling, new tasks are scheduled as early as constraints allow. This means the task is placed at the very earliest time possible, taking into consideration start and end constraints, and dependencies on other tasks. Resource availability is not taken into consideration, so resources may end up overutilized (this is why leveling is an important additional step).

Tasks can also be scheduled as late as possible or locked (with the lock icons above the Start and End dates in the Schedule section of the Task inspector, or by holding Command and clicking either end of the task’s bar in the Gantt chart) so they are not affected by leveling.

When you level the project (or whenever a change is made, if Project ▸ Automatically Level Resources is selected), OmniPlan rearranges tasks which have resources assigned, to make sure no resource is being used at more than 100% of its availability. Tasks moved back by resource leveling are scheduled by resource availability.

During leveling, OmniPlan has to make an educated decision about which task should get access to a resource first, and which tasks should be pushed back by a resource dependency. In judging which task to put first, the following criteria matter, in this order:

1. Requirements to end by a certain time, such as locked end dates, constraints, or being a prerequisite to a task with such a requirement.

2. Task Priority, as set in the Priority column of the task outline.

3. Position in the task outline; tasks that are higher in the outline are scheduled earlier.

Duration is how long a task takes in actual working hours in the schedule. If the task begins at 8:00 and ends at 12:00, that’s a duration of 4 hours. Note that non-working times don’t count; if a task starts one afternoon and doesn’t complete until the next morning, or spans a lunch break, only the working hours are counted. Also note that the resources assigned to a task may have different working hours than the project as a whole, and thus the displayed duration of a task may not match up exactly with the amount of effort it takes.

Effort is the total amount of working time put into a task by all assigned resources. A task with a duration of 4 hours, with 2 resources assigned at 100%, has an effort value of 8 hours. Note that Material resources don’t contribute to effort, only Staff and Equipment resources do.

The duration and the effort of a task can change depending on the resources you assign.

Each task has a setting in the Resource Allocation section of the Task inspector which controls whether to keep the duration fixed, the effort fixed, or both.

When you assign or unassign staff and equipment resources, the value that isn’t fixed re-calculates its value; the other field stays the same. Regardless of which value is calculated, you can always edit either value manually.

If both values are fixed, then assigning resources changes the assigned percentage.

Number of Assigned Resources

Assigning more resources to a task generally causes the task to take less time, because the required effort gets completed sooner.

Efficiency of Assigned Resources

Assigning less-efficient resources to a task causes the duration to be longer than the effort, because the resource takes more time to achieve the same amount of effort.

Assigned Amount and Available Units

Assigning fewer units of a resource to a task causes the duration to be longer than the effort, because less of the resource’s time and energy is being spent on that task. This situation is common when a resource is split between multiple tasks at one time. The amount of a resource you can assign to tasks depends on the resource’s available Units (set in the Resource Info section of the Resource inspector or the Units column of the Resource outline). Assigning more of a resource than is available causes a violation and shows up as overutilization in the Resource timeline.

By default, OmniPlan determines the critical path by taking into account the dependency relationships between tasks, and the amount of free (slack) time there is between them.

• On the dependency side, an unbroken chain of tasks with Finish ▸ Start dependencies represents a simple critical path to project completion. Tasks that are independent won’t be on the path at all, since they can occur at any time during the project.

• On the slack side, hammock tasks or tasks with a set start date before which other work has been completed can lead to periods in the project where nothing is happening. The length of these periods that determine whether the critical path is affected is set in the Milestones inspector.

OmniPlan can display critical paths both for the entire project, and for individual milestones. To turn on critical paths, click the Critical Path button in the toolbar; to choose which critical paths to display, click the arrow in the corner of the button and choose the milestones you want, or choose them in Milestones Inspector.

Choose a date and time (today by default), whether to allow tasks to be marked partially complete, and whether to update all tasks or just the selected ones.

When you click OK, the tasks’ completion percentages are updated to the specified date and time.

Clicking the Reschedule button brings up the following dialog.

Choose a date and time to reschedule the incomplete tasks, and whether to update all tasks or just the selected ones.

When you click OK the incomplete tasks move — and the whole schedule updates — so that work can continue from here.

Note that this only moves tasks with incomplete work that was scheduled for before the date you specify; tasks in the future aren’t affected.

To set a baseline, click the Set Baseline button in the toolbar. You’ll be prompted with a field to name the baseline; the default name is today’s date.

When you click OK, the baseline schedule is set and any further changes are applied to the actual schedule instead.

Choose Split Schedule or Both Schedules to see the baseline and actual schedules together, so you can compare them.

OmniPlan 3 supports not just a single baseline, but as many as you want — so at any given point in the project, you can take a snapshot that sets a new standard from which the actual project can proceed. You can compare a given baseline with the current actual schedule using the Baseline/Actual menu in the toolbar.