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All posts tagged open ends

Why Make Open-Ended Activities Critical?

Categories: Constraints, Critical Path, P6 EPPM, P6 Professional, P6 Tricks, Schedule Options
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Primavera P6 Professional is obviously a very powerful scheduling program so naturally some of its features exceed the needs of the typical project. I have consulted on projects that span as little as 35 hours to as many as 50 years. Different industries have unique requirements for their schedules as well. Primavera P6 is designed to handle a wide variety of projects. Today I would like to address my reasons for using a feature in Primavera P6 that is rarely used by the typical scheduler: Make Open-Ended Activities Critical. You will find this feature under Schedule Options (Tools > Schedule > Options).

The concept of making open-ended activities critical was introduced many years ago in Primavera P3. And for the longest time I dismissed it as a quirky feature surely not applicable to me. After all, why would I promote an activity to critical status solely because it is missing a successor? That seems akin to me declaring myself the winner of a contest that no one else entered.

Some of my colleagues back in the 1980s figured it was an en easy way to identify activities that should not be critical. Okay, that seems backwards, but the idea was that if some task showed up as critical that did not seem “right” the scheduler would investigate further. But Primavera P3 had a report similar to what we call the Schedule Log in Primavera P6 that was a more definitive (and easier) way of identifying open ends in the schedule. With this in mind, making activities that are missing a successor critical did not seem like the best approach to finding open ends.

I started my scheduling career working solely on construction projects so my viewpoints towards Primavera P3 were based on a single industry. Years later, when I began consulting on a wide-variety of projects I realized another purpose for Make Open-Ended Activities Critical. For example, let’s say I am a manufacturer trying to track progress on several production lines. I would like each production line to have its own critical path, or what Primavera P6 refers to as Longest Path. But this would entail making each production line a separate schedule.

It would be a lot easier to track progress, however, if I incorporated all of the production lines into one schedule. That way I would not have to keep opening up another schedule to track progress. And P3 only allowed four schedules to be opened simultaneously. (Some of you P3 users undoubtedly remember the master and sub-project concept from P3 which was another alternative to what I am describing). But how could each production line have its own critical path without creating separate projects?

Yep. Make Open-Ended Activities Critical. See, by not linking the production lines to each other they would all have an open end at the end of their sequence. So every production line now has critical activities. The float values are not based on the longest of all the production lines. Each production line has activities with zero Total Float. Problem solved!

The concept I just described works the same in Primavera P6 as in Primavera P3. You might be thinking that each production line could have a constraint on the final activity to create zero Total Float and then link the final activity in each production line to some final milestone. Yes, that will work too, smarty pants! It also means that additional open ends do not need to be introduced into the schedule.

Another reason for Make Open-Ended Activities Critical is relevant to projects in any industry. One of my clients currently expects his project to finish early. Owners often don’t allow the original plan to show an early completion date because it might become the basis of a claim (“I planned to finish early and you stopped me”). In this situation the owner allowed early completion. So my client inserted two finish milestones in his schedule: “Projected Finish” and “Final Completion”. The latter milestone matched the contractual finish date.

The “Projected Finish” milestone had no constraint since the date could obviously slip without any ramifications. The “Final Completion” milestone had a Finish On constraint (Mandatory Finish also works) so the date could not move at all. But as you might have guessed, this meant that only the “Final Completion” activity appeared as critical in the schedule. The earlier milestone and all of the activities linked to it (directly or indirectly) carried Total Float values based on the later milestone.

A critical path consisting of just one (the last) activity) would obviously be acceptable to no one. But the solution was quite clear to me. While my client had linked the “Projected Finish” milestone to the “Final Completion” milestone (to avoid unnecessary open ends) we need the “Projected Finish” milestone to have no successor. Then, by choosing Make Open-Ended Activities Critical in the Schedule Options the Longest Path of activities leading up to “Final Completion” all had zero Total Float. Bingo.

Below is how the schedule looked with “Projected Finish” linked to “Contractual Finish”. Not having open ends means there is no logical critical path. Also, the “Projected Finish” milestone is a non-driving predecessor to the “Contractual Finish” milestone, as evidenced by the dotted relationship line:

Primavera Scheduling

By deleting the relationship between “Projected Completion” and “Final Completion” and choosing to Make Open-Ended Activities Critical under Schedule Options, the activities leading up to “Projected Completion” are now critical:

Make Open-Ended Activities Critical is not always a necessary feature, but as you can see, it certainly does have a purpose.

 


Dissolving vs Deleting P6 Activities

Categories: P6 EPPM, P6 Professional, P6 Tricks, P6 Web
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We all make mistakes, or perhaps the scope of work has changed, which leads to activities being deleted in the schedule. And most users will simply delete the unnecessary activities. This, however, often leads to open ends in the logic. After all, you might be deleting the only successor to another activity in the schedule, or deleting the only predecessor to another activity. To avoid this problem, I dissolve activities instead.

All of the current versions of Primavera scheduling software have the ability to dissolve activities: Primavera Contractor, Primavera P6 Professional, and Primavera P6 EPPM. But dissolving activities is nothing new, as Primavera P3 incorporated this feature many years ago. Regardless, many P3 users ignored the feature and continue to do so in the current programs.

So what exactly does “dissolve” do? Well, when you dissolve an activity its predecessors are linked to the successors of the dissolved activity. Say for example that Activity A precedes Activity B, which in turn precedes Activity C. Dissolving Activity B would result in Activity A becoming a predecessor to Activity C. In theory this should be an acceptable change to the logic, since Activity A was already an indirect predecessor to Activity C.

Here is an example of how the dissolving process works. In the screenshot below I have three activities, each with a duration of 5 days, linked together using Finish to Start relationships. So the total amount of time required for these three tasks in 15 days:

Dissolve Activity_1

 

In the next screenshot, I have highlighted Activity B and then right-clicked to select dissolve from the menu:

Dissolve Activity_2

 

Now that Activity B has been dissolved, Activity A is a predecessor to Activity C and the total amount of time has been reduced to 10 days:

Dissolve Activity_3

 

Easy as pie, unless I’m the one baking it. While it is always a good idea to check the Schedule Log for possible open ends elsewhere in the schedule, there should be no open ends as a result of dissolving activities.

Any questions? Feel free to contact me.

 


Using a Filter to Find Missing Logic

Categories: logic, Primavera P6
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One of our training clients recently asked us to create a rather unusual filter showing “open ends”, or activities that are missing predecessors and/or successors. While this information can be gleamed from the Schedule Log (Tools > Schedule > View Log) this report does not graphically represent these activities. A filter will of course allow us to show these activities on the Gantt Chart, so that we know when and where these activities occur in the schedule.

In the screen capture below I have created a simple filter to display activities with open ends. Notice that I have two lines in my filter and that I have selected “(Any of the following)” when combing the two specified parameters. The first row asks P6 to list activities where the predecessor value is blank. You might know that we can display predecessors as a column in the Activity Table, and if there are no predecessors for an activity then this cell would be empty.

In the second row I have added the same statement for the successor value. The only thing left to do is make sure P6 understands that I want activities that are missing predecessors or successors. In other words, if the first row or the second row statement is true, give me those results. To do this, I selected “(Any of the following)” filter parameters:

 

Filter for Open Ends

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As you can see, setting up the filter is pretty simple. Leaving the value blank does not work in many situations, but for predecessors and successors this approach is fine.