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How to trace the Critical Activities

22 replies [Last post]
Sat, 2009-06-27 02:14
Aryan Yap
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Hello Everybody,

Can you please advise me how to trace and show Critical Activities?

Here are the scenarios:

We have about 2000 activities in our programme. However, we are already behind by 4 months (112 days) based on current schedule against baseline.

The Client asking me to submit weekly the critical activities based on current updated programme. What I did, in order to trace my critical activities I applied the constraint to all my milestone finish date (Finish on or before Constraint). Because what I know, this is the only way how to trace critical activities. Since our Client, does not allow us to put the "Project Must Finish By" date.

My main problem is, the Client again does not allowed us to apply the constraint in the milestone as well as in the activities.

My question is, is there any way, how to show the critical activities in the current schedule? I tried to remove the constraint; however the current schedule gives me only 5 numbers of critical activities which is not correct.

All suggestions are welcome especially to the experts.

Thank you and best regards,

Aryan
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Replies

Tue, 2009-06-30 10:55
#1
Rafael Davila
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Vladimir

Either through manually or computerized resource leveling, all CPM/PDM software packages should identify Resource Critical Path and particularly show the "true" total float under resource constraining. Although I still question if there is such a thing as an absolute resource critical path my definition is based on the critical path as determined by your resource constraining algorithms. I still cannot believe over 1GB/ (1,000MB) inefficient software packages like PXX cannot do it while Spider Project a powerful software package of about 30MB (estimate based on the demo version) can handle the issue. Unfortunately some of us must follow the pack and use what others are using. Keep on calling the attention, hopefully others will follow.

At home we generally use Mike’s approach for resource leveling rather than using the computerized leveling algorithms available in our software, that at times generate weird results. Blame it on our software if you will. Sometimes for small jobs even without resource loading the job, we account for limited resources through logic only, even when prohibited by few specs. For these I usually do equipment and manpower resource loading on my own, manpower loading by defining crews instead of going to trade details, with this I verify for resource overrun and if necessary call it to the attention of the contractor. For this purposes I believe all software packages should provide a way to easily identify “soft” dependencies you can toggle on and off as need be, I am not sure but believe Spider Project do provides this functionality.

I like the idea of being able to identify Resource Critical Path and get "true" total float as I believe a combination of both methods, manually and/or computerized resource leveling, is a viable alternative. Having the option of the software doing the resource leveling should always be open.

Best regards,
Rafael

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Tue, 2009-06-30 08:43
#2
Vladimir Liberzon
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Activity has zero total float if the delay in its execution postpones project finish. In resource constrained schedule activities have resource constrained floats. Activities may be delayed due to resource, supply, or financial constraints, not only links.
The sequence of resource critical activities (with zero resource constrained floats) is Resource Critical Path or Critical Chain.
It is easy, though most packages calculate show wrong total floats in resource constrained schedules.

And I don’t believe in manual resource levelling for large projects, you know.

Regards,
Vladimir
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Tue, 2009-06-30 08:15
#3
Mike Testro
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Hi Vladimir

We have had the resource levelling discussion before - you recall that I would never let the software do it for me.

In any case I do not see how resource levelling can create a critical path without any links.

Regarding resource links I was refering to specific resource types that will not necessarily fluctuate wildly.

My real life example were the 3 avaiable cable joiners.

Best regards

Mike Testro
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Tue, 2009-06-30 05:34
#4
Vladimir Liberzon
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Hi Mike,
you wrote: The only way is to put links between the sections but there has to be a valid reason for the links.

If you will put links basing on resource availability then these links shall be reconsidered if and when resource availability will change. It may happen many times and in large schedules that you prefer implementing such changes is a nightmare. Why not to apply resource levelling without defining artificial links?

The critical path in resource constrained schedule we call Resource Critical Path - it may include activities that are not linked at all. Critical Chain is another known name.
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Tue, 2009-06-30 03:12
#5
Bill D.
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mr Mike,

Thank you for clearing this up,

cheers,

bill d.
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Tue, 2009-06-30 02:42
#6
Mike Testro
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Hi Bill

I said in an earlier thread that sections will have their own integral critical path - this happened on my cable pulling project.

One sort of link between sections may be a key resource such as cable joiner.

When there are only 3 such skilled workers on the project then that could be a link between sections.

Cash flow could be another.

How to weigh the magnitude of each section?

Even if you could I do not see how that would affect the overall criticality.

The only way is to put links between the sections but there has to be a valid reason for the links.

Best regards

Mike Testro
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Tue, 2009-06-30 01:36
#7
Bill D.
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Mr Mike and others,

I agree that there will be no overall critical path to the pool of stand alone sections if it is not really related, however, I also believed that the stand alone sections by themselves creates a critical path of thier own.

The question is,
1)how can you know the level of importance on the series of critical activities in each and evry stand alone sections?How can we weigh its magnitude?
2) if the stand alone sections have no logical linkage between them ,how is it possible, if they belong to a single project and single contract.

My opinion is they can be interellated at some point, ..even at the lowest possible means, if they are owned by a single project/contract.

I maybe missing something here, sorry if these is not so relevant the first post.

This query is for clarification...

Thnx and Best regards,

bill d.
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Mon, 2009-06-29 05:03
#8
Aryan Yap
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Hi Gary,

You are absolutely correct..100% I agree with you. That is what I am looking for.

Let me explain more clear what I did in our current schedule.

I applied primary constraint (finish on or before) in the Milestone finish date 30-Dec-2010 in the updated current schedule. However, our current updated schedule finish date is on 30-Apr-2011 due to the delay. Now, the total float of this milestone is -120 days. The predecessors of this milestone will also be affected due to constraint.

My purpose here is to show only the critical activities which I know that this milestone is lying in the critical path.

My question is, is this possible or acceptable?

I know that constraint will have a huge impact during the preparation of delay analysis and have a significant effect on risk analysis result.



Mike,

I agree with you with regards that some activities have link to incorrect successor but there are only two activities does not have relationship (Start and Finish activities of the project).

As we know, the Forward & Backward calculation, say for example Activity A has a finish date of 23-Oct-09 and Late Finish is on 15-Mar-10, the total Float equal to LF - EF = 134 days.

Thank you and Best Regards,

Aryan



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Mon, 2009-06-29 04:09
#9
Bill D.
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Mr. Mike,

the 6th line of your post "I have been involved in projects where there is no critical path at all" is really a pumping statement that i would like know, on to how and why this can be possible?????????


Please lit a light on this one.

Cheers,

bill d.
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Mon, 2009-06-29 04:53
#10
Mike Testro
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Hi Bill

Where there are a number of stand alone sections in a project with a single completion date it is most likely that there will be no overall project critical path.

One such that I was engaged in was cable pulling on the London Underground where work possessions were given for each section - sometimes quite randomly - with no logic linkage between them.

Best regards

Mike Testro
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Mon, 2009-06-29 03:50
#11
Vladimir Liberzon
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Aryan,
comparing current version with the baseline you will see the delay. It is not necessary to set target date for estimating the delay.
If you have the single end point in your schedule (all activities precede finish milestone) then the target date for this single finish milestone only can be set.
In your schedule this finish milestone will have some float (negative). All activities that have the same float are critical.
But check that you have no hanging activities (that have no successors) in your schedule. If such activities will be found examine if these activities really can finish after all others. Usually there are missed dependencies, but if they really do not have successors link them with you finish milestone.
Regards,
Vladimir
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Mon, 2009-06-29 04:25
#12
Gary Whitehead
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Aryan,

Without any constraints, Primavera will calculate total float (and hence criticality) based on EF=LF of the final activity in the project. If you want a different target completion than that, you have to use a constraint.

I don’t know P6 well enough, but you may be able to set up a filter which shows only those activities where by the difference in early finish vs baseline early finish is greater than the baseline total float for that activity. Assuming no logic changes in baseline vs current, this should give you your critical activities.

Or if you know the project completion is 116 days late vs baseline, filter for activities where total float is less than (116 plus terminal float of baseline project)

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Mon, 2009-06-29 03:44
#13
Mike Testro
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Hi Aryan

If you are getting float lengths of up to 100 days then there are insufficient FS links to successor tasks.

How many activities have no outgoing links?

Are they going to the correct successor?

Have your 5 critical tasks been set to ALAP position?

I have been involved in projects where there is no critical path at all.

It may be that your project is similar - are there lots of stand alone sections that have no logical linkage between them?

Each section would have its own internal critical path but not contribute to the whole.

Try rescheduling on the brach or subchart only.

Best regards

Mike Testro
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Mon, 2009-06-29 03:18
#14
Aryan Yap
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Hi Vladimir,

I cannot figure out the critical activities without applying the constraint. We need the target finish date in order to monitor the delays in current schedule against baseline.

Calendar is not an issue because we used only one calendar (6 days per week).

As I mentioned earlier, if I am not going to put any constraint almost all remaining activities has a total float of more than 100 days. So, I think it is not normal for a project having been delayed for 4 months with big amount of floats.


Mike,

The Client doesn’t like to change the logic especially for the dependencies of all activities. Even though I set my total float equal to 5 days, still I am getting the wrong result. We are trying to compare the baseline against current schedule to monitor the delays in the project as well as the critical activities.

As we know, every weekly update the critical activities are also keeps on changing due to site condition. Especially for those activities supposed to start. You can try these things out using P6 and you will find out what I want to elaborate further.

Vladimir, Mike please correct me if I am wrong but until now I cannot figure out how to show the critical activities in the current schedule without applying the constraint.

Can anybody help please…

Thank you & Best Regards,

Aryan
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Mon, 2009-06-29 02:18
#15
Mike Testro
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Hi Jose

Your thread was deleted because your attempt at an explanation was:

1. Inexplicable
2. Unfinished because you had to get to the club.

Have another go please but keep it concise.

Best regards

Mike Testro
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Mon, 2009-06-29 02:16
#16
Mike Testro
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Hi Aryan

Another problem may be that your progress date has been set later than links with lead lag times.

For isnatnce if you have a task that is 40 days long and a SS lead lag of 15 days and progress is set at 50% then you will have lost the SS link and all criticality relating to that link.

Also as Vladimir states - different calendars will react differently - so try setting your criticality to 5 days total float - not Zero.

Best regards

Mike Testro.
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Mon, 2009-06-29 01:37
#17
Vladimir Liberzon
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Hi Aryan,
I do not use P6 and my proposal is not based on this software features. But I think that it is applicable to any PM software.
Forget about target finish date. Remove all schedule constraints (finish not later than, start not earlier than, etc.) and calculate project schedule. This schedule will show your plan from the current date and total floats in this schedule. Pay attention to the calendars. If different activities and resources have different calendars then the schedule may include delays caused by different working times of some activities and resources. In this case estimate potential delays caused by this difference and define activities to be critical if their total floats are less than ... days.
Inform us if it helped.
Best Regards,
Vladimir
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Mon, 2009-06-29 00:48
#18
Aryan Yap
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Hi Mike,

As we know the critical activities if the total float <= 0. The Client do not want us to apply the constraint and to put the “Project must finish date” But they wants us to show the critical activities based on the updated current schedule.

I tried to apply the constraint on the milestone, as we know contractual milestone cannot be modified without prior approval. And it works fine, showing the zero and negative float. Now, I tried to removed the constraint however, my critical activities has only 5 Nos. and it is not correct because, as I mentioned in my post #1 the project was behind by 4 months (112 days) based on current schedule against baseline.

The Contractual Milestone finish date is on Dec. 30, 2010 and the updated current schedule is on April 30, 2011 due to the delay.

Our Client required us to submit the critical activities every week. Can you please advise me how to show the critical activities in the updated current schedule using P6 V6.2.1 without applying “constraint” and “project mush finish date”?

Can anybody advice me...

Best Regards,

Aryan
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Sun, 2009-06-28 09:48
#19
Mike Testro
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Hi Aryan

Constraints will affect the critical path.

Save your file.

Filter on all activities with restraints.

Remove ALL restraints.

Adjust the logic so that every task has at least 1 predecessor and 1 successor link.

Re Schedule - now filter on the critical path.

Best regards

Mike T.
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Sun, 2009-06-28 12:02
#20
Jose Ramirez
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Dear Moderator (i.e. Mike T),

I wanna know why my post to help the dude with this Q was deleted? I was just trying to be helpful and show him how is done.

Is there something i am doing wrong in this forum or any man law that i am violeting. Since, none of my Q get answered & now my post are getting deleted.

I have read much more useless information on this forum which has not been deleted yet?

Please, let me know.

Anyways, I still love this forum and i am pretty new on posting things here, and continue to be a member for a very long time.

Sincerely yours,



"ii got dem diamOnds’ 0n ma neck, gOt patrOn iin ma cup, iif u want iit cOme & get it shawty ii dOn`t giive a ****` ♪"



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Sun, 2009-06-28 00:17
#21
Aryan Yap
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Hi Vladimir,

Thanks for your quick response. I am using Primavera V6.2.1

Perhaps you can help me regarding this issue. Is there any problem if I apply the constraint in the milestone, what will be the effect for the overall project’s condition?

Thanks in advance.

Best regards,

Aryan
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Sat, 2009-06-27 08:47
#22
Vladimir Liberzon
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Hi Aryan,
you shall speciy what software do you use.
We have no problems with showing critical activities in Spider Project schedule. I think that your problem is software specific.
Regards,
Vladimir
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