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stephenrussett 2010-02-15 08:07 PM

Critical Path Question
I am having some issues with the Critical Path. When i run critical path, the very last 2 activities and final mile stone get marked as critical path, but nothing else connected through dependencies gets marked as critical path. What would cause this in omniplan?


skwirl 2010-02-15 08:37 PM

The critical path is the series of dependent tasks which, if any of their durations change, will cause the whole project's duration to change by pushing out the last task in the project.

Not having your project in front of me, here's a few things you can check in your project:

Make sure your tasks are connected by dependency connections. If they're not, a task that's delayed by a little bit may not delay your project end date and won't be considered a part of the critical path.

If a chain of dependent tasks have some gap of time between one another that can break the critical path. The reason for this is because if there's a gap of time, that means the task technically has some wiggle room before it starts to affect the project's duration. Once you close that gap of time the critical path will be visible again. How do you close up the gaps in time? That involves the task's scheduling setting which I'll explain below.

By default, all newly created tasks are set to start "As early as constraints allow". This is why new tasks automatically start at beginning of your project and not on the current day. Now, if you use your mouse and drag a task in the gantt chart to set a new start date or if you enter a start date manually into the start date field of the task, the scheduling is changed to start "On specified date". It's anchored to that start date and won't show up on the critical path that task won't move automatically anymore regardless of dependency connections, leveling, etc... You want to make sure all your tasks are set to start "As early as constraints allow" for it to be part of the critical path. If you have a task that has been set to start "On specified date" you can click on the "reset" button in the Task : Information inspector.

Does this help? If you're still seeing issues with the critical path in your project, you can email us your OmniPlan file to [email][/email] and we'll take a closer look.

stephenrussett 2010-02-15 08:41 PM

Ok most likely in this case then i have a few activities which are locked in dates. These dates cannot occur as early as possible. They have to be exact dates. Will the critical path not continue through the locked in date?

stephenrussett 2010-02-15 08:44 PM

Also what would be the gap of time that OP considers wiggle room?

would 1 day be wiggle room? Is there any way to change this?


skwirl 2010-02-15 09:18 PM

[QUOTE=stephenrussett;73364]Ok most likely in this case then i have a few activities which are locked in dates. These dates cannot occur as early as possible. They have to be exact dates. Will the critical path not continue through the locked in date?[/QUOTE]

The critical path will not continue thru a locked date because with the date being locked, nothing before the locked task can delay the locked task's start date. (Similar behavior to having a task set with a "on specified date" schedule).

[QUOTE=stephenrussett;73365]Also what would be the gap of time that OP considers wiggle room?

1 second is considered wiggle room. In other words, there's zero slack time for critical path currently. We have a feature request to allow the slack time to be a user-definable setting which I'll add a vote for you.

stephenrussett 2010-02-15 10:04 PM

mmmmm we really need a way to see the critical path even with locked in dates. :(

whpalmer4 2010-02-16 04:39 PM

3 Attachment(s)
The critical path is the set of all the tasks which if delayed by the scheduling quantum will delay the completion of the project. When you work your way backward from the end to the beginning, if you come to an "air gap" in the timeline, whatever is between that point and the beginning of the timeline is not on the critical path unless something prior gets delayed by enough to close the gap. If I have to do something by Friday, but can't start the final step until Wednesday (and it will take all of my time from that point until the deadline to complete it), the steps I can do on Monday are not on the critical path unless I don't get them done before Wednesday. I can blow them off until Tuesday without impacting the completion of the sequence on Friday. They are not on the critical path of the schedule. The task on Wednesday will delay the completion on Friday if it starts late, so it is on the critical path.

I do agree that it would be nice to be able to tell OmniPlan that such gaps below a certain length should be treated as non-existent so that you can more readily determine what is likely to be the effective critical path. If Joe Programmer has to finish his widget prior to integration starting Monday morning at 8AM, the fact that he's scheduled to complete his work the preceding Friday at 4:55PM doesn't leave much room in the schedule for unpleasant surprises before his task really is on the critical path. On the other hand, if he's scheduled to complete his work two weeks earlier, he could do quite a bit of extra posting on the Omni forums without affecting the date the product ships. A suitable value for the fuzz factor is clearly going to depend on the project plan; what is a suitable value for the multi-year OmniPlan 2.0 effort is going to be a bigger value than would be appropriate for my two-day plan for preparing a big holiday feast.

You can (tediously) work around this behavior of OmniPlan's by putting in dummy elements before and after such a gap and linking them with dependencies. This allows you to run the critical path around the item with the fixed start date. I've attached a sample file showing an example of this, and two screen shots (one with the dummy elements, one without).

stephenrussett 2010-02-16 04:56 PM

I agree with you. But at the same time, there are really two types of Critical Paths people want to see. First they want to seethe critical path for timeline just like it is currently. But we also want to see the critical path that is the path is has the direct line of dependents back to project start regardless of timelines. Point is that if there was a weeks worth of wiggle room/slack or even a hour. We should be able to tell OP to disregard that. I should be able to see the CP without any concern for slack.

On a side bar would be nice if we could add a default lead time for activities. As realistically no one will ever finish on project and start the other immediately. There is ALWAYS a delay. wether it be 10min or 2 hours.

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