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How to create different Critical Path

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Andrea Giordano O...
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hi everybody,

  I would like to do 2 critical path in the same schedule, for 2 different unit in the same plant , how is possible to apply on P6 ?

 

thanks in advance

Andrea  

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Stephen Devaux
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I'd suggest that much of what's wrong with project management is due to crappy definitions. For example, the PMBOK Guide definition of "project" is "a temporary endeavor to create a unique product, service or result". Apart from the weasel word ("endeavor"); apart from the vague adjectives (what DO they mean in this context, exactly?); the definition fails to explain ANYTHING about why we do a project! And that failure obscures the criteria that should guide decision-making.

ALL projects are INVESTMENTS, and, as with ALL OTHER investments, should be judged on the basis of expected ROI. And decisions should be made on the basis of increasing the ROI for the investor(s).

To define projects otherwise is like defining ice hockey without using words like game, sport or contest! Without that defining term, even the greatest skater engaging in ice hockey would have no idea what to do!

Similarly, the critical path is NOT the activities with zero float; or least float; or most drag; or even the path whose durations add up to the greatest amount.

The ACTUAL critical path (ABCP?) is the path that determines the length of the project! And that's why it's SO important! It's what turns out to be the longest path of activities, lags, resource insufficiencies, constraints of ANY type, delays, and even periods of inactivity (all of which can have drag!). And what we plan at the start is the PLANNED critical path, which often does NOT wind up being the path that determines the project duration.

The failure to define critical path in that way is, IMO, THE major reason that methodologies that don't attempt to plan it (i.e., agile) have developed -- because ignoramuses don't understand its importance and the need to try to plan and manage it. And, Lord knows, it's MUCH easier to not have to perform that due diligence!

Fraternally in project management,

Steve the Bajan

sharief sheikh
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If we have linked the activities correctly, then P6 would be able to give multiple critical paths in the order of float. You can use the advance tab of scheduling options to set this... once set and run the schedule then use Group and Sort option to display the activities based on the 'float path order' i.e group by 'float path order.' By this you would be able to see the critical as well as near critical paths for the selected network path. Make sure you select the finish milestone of the schedule under 'Display multiple float paths ending with activity' to review criticatl paths for the overall project.

Rafael Davila
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You might already have other critical paths consisting of a different set of activities and different activity timing but you do not know it.

It is often possible to employ alternative resource allocations resulting in schedules with identical overall duration but different timings for individual activities; in one schedule an activity may be critical but in another it may have significant float, total float is activity and schedule property.  This “nonexistent” total float in some alternative schedule is often referred to as Phantom Float. 

Phantom Floats can be defined as the difference between current schedule activity start and the possible activity start among all possible equivalent schedules. It is possible the activity might start earlier in one schedule while in another schedule it might start latter than in current schedule. It might not be practical to quantify all phantom floats because of the NP nature of the calculations. Dealing with Phantom Float has been a challenge for decades.

The RCPM proposed by Jesus M. de la Garza could be a start on our quest to tame alternative schedule floats.  I believe we shall keep under separate fields current schedule floats and alternative schedule floats.

We must acknowledge the possibility of the alternate schedule sequences and Phantom Float or we might end up making our decisions using incorrect scheduling information.  To better manage current schedule float and phantom float as well; specifications shall mandate resource-driven schedules as opposed to task driven schedules.

The longest path is broken when activities are no longer driven by relationships; that is, when activity dates are driven by constraints or resource leveling.  Longest path calculation includes interproject relationships.  Therefore, activities designated as on the longest path may change depending on whether you schedule a project alone or with its related projects.  If a project has interproject relationships and you schedule it alone, the interproject relationships are treated as scheduling constraints.  The longest path theory was devised for old CPM when resources were assumed unlimited, it breaks under resource constraints.

It is time to let Longest Path Theory rest in peace and require resource-driven schedules take over.

Dwight Carter
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Thanks for such a great topic! Will use it further.

foji babloo
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Hi Guys, I sthere any other way to identify critical path other than these 03 options: 1- Total Float is less than or equal to (any value xyz)2- Longest Path3- By calculating ''Multiple Float Paths'' Please share if you have any other option or procedure to identify critical path in p6.
Divya Sethi
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There are six steps in the critical path method:
  1. Step 1: Specify Each Activity. 
  2. Step 2: Establish Dependencies (Activity Sequence) 
  3. Step 3: Draw the Network Diagram. 
  4. Step 4: Estimate Activity Completion Time. 
  5. Step 5: Identify the Critical Path. 
  6. Step 6: Update the Critical Path Diagram to Show Progress.
Rafael Davila
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I wonder if setting all open ends as critical will make the resource leveling algorithm to yield undesired results when resources are shared among the different paths.

Rafael Davila
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As a general rule, every activity in any CPM schedule – except the start and finish milestones – must have at least one predecessor and at least one successor.   Dangling activities not meeting this rule – also known as open-ended activities – indicate inadequate schedule logic.

When you have multiple start and/or multiple finish milestones you will have multiple dangling milestones and the rule might not be broken.  Just make sure every activity, except start/finish milestones are linked to a path leading to the appropriate milestones.

Keep in mind longest path gets broken under resource leveling, constraints, interproject relationships (treated as constraints).  https://docs.oracle.com/cd/E17462_01/Web_Access/Help/en/Projects/Tasks/pm_cpm.htm

  • Longest path defines the sequence of driving activities that determine the project end date.
  • The longest path is broken when activities are no longer driven by relationships; that is, when activity dates are driven by constraints or resource leveling.  Longest path calculation includes interproject relationships. Therefore, activities designated as on the longest path may change depending on whether you schedule a project alone or with its related projects.  If a project has interproject relationships and you schedule it alone, the interproject relationships are treated as scheduling constraints.

Not all project milestones have a target finish date, in such case the finish milestone is not date constrained. If you want to see independent resource critical path for these milestones as well as activities float that will not delay the milestones this setting (make open-ended activities critical) should do it.  

When you set finish date constraints in P6 it can create negative float values, negative float is information that helps to analyze project status but is useless for project network analysis. The workaround recommended by experienced schedulers in such software is to temporarily eliminate the constraints plus other remedial actions that might include setting open-ends as critical. 

Primavera P3 users could resort to Zero total float constraint - Use a zero total float constraint to make an activity critical. When you impose a zero total float constraint, P3 sets the late dates for the activity equal to its early dates, giving it zero total float.

P3 had more and better implemented constraint options than P6.  Noteworthy are date constraints only used when they create a tighter schedule. Only nefarious mandatory constraints would create negative float.  Mandatory P3 constraints were used only temporarily for purpose of analysis.

https://docs.oracle.com/cd/E20557_01/documentation/P3/P330ref.pdf

On the other hand Spider Project can display negative float without use of nefarious mandatory constraints or date constraints that would mess with late dates as P6 does.

Zoltan Palffy
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you can make open end critical but techanically there sould only be 1 open end which is the last activty in the schedule

Rafael Davila
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P6-make-open-ended-activities-critical
Andrea Giordano O...
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Thanks again for your answer, Im just checking reliability of schedule, cause has still to be defined by contract and im preparing tentative baseline.

Zoltan Palffy
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the other option is to change the float value range that determines when something is critical.

In P6 

open your project 

go to the Projects directory and make sure your project is highlighted

Click on the Settings tab

under the section Define Critical Activities

Select Total Float Less than or equal to and then on the right put in the number of days that you want to set that threshold at.

The default is 0 days. 

Andrea Giordano O...
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Thank u very much Zita,

ciao

Andrea

Tom Boyle
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There are several ways to identify multiple critical paths in a P6 project schedule.  https://boyleprojectconsulting.com/TomsBlog/2017/09/16/multiple-critical-paths-in-a-single-cpm-schedule/

Choose one:

  • Multiple Float Paths
  • Super-aggressive late constraint
  • Super-long trailing dummy (with Longest Path).

Good luck, tom

Andrea,

Not sure what you mean to create 2 critical path in the same schedule, since critical path is the longest path or one with "limited float", so to attain 1, 2 or more critical paths on same schedule; its better to set constraint date to the last activities of those series of activities  or you can connect the last activity to a common milestones and then the the series of activities with more float than the other you can set a "LAG". This way you know that all these activities belong to your "critical path".

 

In P6 there is an advance option for scheduling, I am not sure if this is what you mean. This gives you an option to have amount of schedule scenario for achieving certain "milestone" (this is advisable if you have a very complex network of activities. This helps planner to focus on certain amount of activities only...>>>i cannot embed a picture to show this but if you have p6, go to schedule (F9), and click on ÖPTION, and second tab is ADVANCED, and there you can opt for Free Float or Total Float calculation for number of paths (series of activities) as you wish.