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Actual Finish vs Finish date (Should I use constraint date?)

13 replies [Last post]
Rizwan Siddiqi
User offline. Last seen 6 years 42 weeks ago. Offline
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Fellow Planners,

 I am new to PV so you guys will have to humor me for a bit.

Have a question about my finish date in the plan I have just created in PV. If a task gets completed earlier than "finish" date, when I put in the actual (and schedule), the finish date understandably changes to the actual date. However, all of the following task dates that are dependent on my completed task also get pulled in (when i schedule).

For example:

Task A - Finish Date 17th

Task B (Dependent on Task A FS) - Start date 18th

Task A Actual Finish - 12th .....Task B start will change automatically to 13th.

While Task B is dependent on A, it is a different team that I would have speicifically reserved to start work on the 18th and I cant have them start work on task B on the 13th  just because Team A for Task A finished earlier.

Note, I do not need baselines for this project so cant go off of baseline dates. 

 

Given my situation, do I need to apply start constraint dates to all of the Task B type activities (which are all of them)?? I dont like constraint dates but let me know if that is what I need to do in this situation.

Thanks in advance

Riz

Replies

Rizwan Siddiqi
User offline. Last seen 6 years 42 weeks ago. Offline
Joined: 15 Nov 2012
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Hi Raymund. 

Nope...dont need it in just Gantt Chart . Need it in Gantt Chart and the Task Information version of ms project. But not sure why that is of consequence?

Need dependent tasks to not get pulled in when predecessors get completed. They are predecessors still because dependent tasks do get pushed OUT if predecessors are delayed, just not pulled in if predecessors are earlier finish.

Surely there is a clean way to do this?

Thanks everyone for trying to get this answered.

Riz

Raymund de Laza
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Joined: 23 Nov 2009
Posts: 700

Do you want this to be presented in the Gant Chart ONLY?

Only UDF can do that customized presentation.

Rizwan Siddiqi
User offline. Last seen 6 years 42 weeks ago. Offline
Joined: 15 Nov 2012
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Hi Rafael and all,

Nope, think I may have not explained myself well enough. I am super glad I dont have the problem I believe you are giving the solution for. Task B doesnt have 2 different resources working on different dates, Task A has team A, Task B has team B.

I would like to quote you the example I quoted joel as well,

As an example, the team that has ownership of constructing something (Task B) cannot do so unless the team that is responsible for procuring the material (Task A) gets done. Therefore they are FS. However, if Task A gets done earlier, PV pulls in the start date for Task B....essentially saying if you've procured the materials earlier, go ahead and start the construction. Practically speaking that would not happen. Construction would start as scheduled regardless of when the materials were successfully procured.

The above is an example. Alot of my other tasks could also fall under this. For instance, I could say until the real estate team procuring the land hasnt done so (Task A), we would not be able to finalize a deal with the local vendors (Task B) since "local" could change if the land location changes. Therefore Task B is FS to Task A. But should that mean if the real estate team finishes their task earlier the contract with local vendor should start earlier? No, cause we would have pre-booked the corporate lawyers meant to help us with the contractual T&C with the local vendor and work on it would have to start as planned (not earlier).

Basically, I am saying tasks on my plan are FS cause they're dependent, but I dont want PV to pull tasks in if a task finishes earlier.

Thanks for your help.

Riz

Rizwan Siddiqi
User offline. Last seen 6 years 42 weeks ago. Offline
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Hi Joel,

Yes, there are different teams however the tasks are dependent on each other. As an example, the team that has ownership of construction something cannot do so unless the team that is responsible for procuring the material gets done. 

So I believe (by my understanding) it is a FS. However, if the team responsible for procurement the material gets done earlier, that should not mean the construction team will start earlier too.

Practically, the construction start date should remain the same even though the material was procured earlier than anticipated.

Note, these are examples are not the exact situation...but its close.

Thank you,

Riz

Raymund de Laza
User offline. Last seen 9 hours 49 min ago. Offline
Joined: 23 Nov 2009
Posts: 700

Rizwan,

That is a customized Update.

1367
riz.jpg

Rafael Davila
User offline. Last seen 5 hours 37 min ago. Offline
Joined: 1 Mar 2004
Posts: 4781

Do you mean that tasks B are assigned different teams and that each team can work independently of each other and that each team will be assigned when all members of the team are available to work on the activity calendar?

This would mean modeling of shift work, even if the shift of each team is for the same hours it is shiftwork in the sense each team do not necesarilly work on the activity during the same days.

To my understandong P6 is poor with the modeling of shift on a single activity and you must either separate the shifts into different activities or manually assign your resources using bucket planning what is probably what you are doing.

Some software cannot correctly model shift work when the duration of the activity is driven by
how much work is produced by the resources on different shifts. 
You can try yourself a simple scenario.
Activity 1 500cm rock excavation
Resource 1 production 10cm/hr  and works Monday, Tuesday and Wednesday 10hrs/day
Resource 2 production 15cm/hour and works on Wednesday, Thursday and Friday 10 hrs/day
If activity starts on Monday:
Monday =>> Resource 1 will produce 100 cm
Tuesday =>> Resource 1 will produce 100 cm
Wednesday =>> Resource 1 will produce 100 cm
Wednesday =>> Resource 2 will produce 150 cm
Thursday =>> Resource 2 will produce 50 cm in about 3 hours
Activity will take 3 days 3 hours.
If activity starts on Wednesday : 
Wednesday =>> Resource 1 will produce 100 cm
Wednesday =>> Resource 2 will produce 150 cm
Thursday =>> Resource 2 will produce 150 cm
Friday =>> Resource 2 will produce 100 cm in about 7 hours
Activity will take 2 days 7 hours.


If your software is not capable of modeling the above, simple shift work on a single activity, then you are using the wrong tool. Every time the activity is delayed, the distribution of work is shifted, when you have many such activities and work on different hour shifts, different days it can become quite complicated. For a single shot you can use incapable software with manual distribution of work among shifts for anything else distributing work by hand is nuts.
 

The following video is a live sample of a similar case of teams working on different days on the same activity.

https://www.youtube.com/watch?v=Gjw2jvsUVyY

Photobucket

Regards,

Rafael

Joel Gilbert
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Posts: 166

If I understand correctly task A and B has different team, then your logic is wrong. Task B is not FS with A it is SS with A as 2 different teams can start at the same time and work independently or you have 2 start constraints and 2 finishes and therefore 2 critical paths. That is the easy way out without creating 2 calendars

Rafael Davila
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Rizwan Siddiqi
User offline. Last seen 6 years 42 weeks ago. Offline
Joined: 15 Nov 2012
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Hey Guys,

Thank you for getting back to me.

Johannes,

Will keep what you said in mind. Basically you are saying make them 99% till the date comes along that it was supposed to finish on. The only issue with this would be when I print my plan for status meetings with stakeholders, they would question why something is 99% when all my other reports would be reporting "Task Completed"

 

Gary,

Your first option, creating a calendar would not be possible since I have multiple tasks throughout the project lifecycle assigned to them (and other such resources), and creating a calendar for each team with working days just for their assigned tasks would be impossible to update.

For your second option, I may need more explanation please. After I input actual for Task A, I should filter the dates to see which tasks have early start (I assume i can get early start without having set the baseline) earlier than the date that the task was originally supposed to start, and then put an early start constraint (havent tried this yet) to bring it to where it needs to have originally started ? I feel like thats a round about way of putting constraint dates isnt it? Also, Task B may succeed Task C and so on which means all the tasks would be pulled in (with early start). This would essentially create the early start constraint on each task that is in the path of Task A. Again, would constraint dates right from the start achieve this better?

I may have completely misunderstood your explanation in which case please excuse me rambling on.

Thank you again for your help guys,

Riz

 

 

Johannes Vandenberg
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Joined: 21 Jan 2010
Posts: 217

Hi Gary

As you mention in your post, you have never come across with this situation. Neither have i but some time ago i stumbled in this situation with one of my junior schedules. He was updating  an schedule and he reported ahead of progress on the activities of the production engineering department. This triggered the prefabrication activities to be starting earlier than planned. The original schedule  for the project was carefully balanced with regard to available resources in the fabrication facility. Plate and profile  cutting  machines are also balanced to generate batches of work of weekly intervals workloads. This also triggered the overall manpower resources at the portfolio level to become unbalanced. So instead of having one batch every week their were now 3 batches to be worked on and thus showed an overload while this was not intended. So  i decided to  make the activity 99 % completed and leave the remaining duration such that the work packages were completed just in time. As we use Earned Value Techniques for all disciplines the CPI for the production engineering was correct within 1 %. I have not opted for the constrains solution because each prefab activity has 25 successors . In any case, i very seldom use constrains in my schedules. So i schedule just in time and running ahead of schedule on occasional activities is not recommended.

Regards Johannes

 

 

Gary Whitehead
User offline. Last seen 15 weeks 6 days ago. Offline

Johannes,

 

I am curious: Why do you recommend using false remaining duration on the predecessor as opposed to a constraint on the sucessor?

Gary Whitehead
User offline. Last seen 15 weeks 6 days ago. Offline

Riz,

 

If the Task B team can only work on specific days, create a caledar with only those days set as working days, and assign it to Task B.

 

If Task B team can actually work on any day in the standard calendar, but you need x days lead-time to change their dates, then:

1) Apply your actuals to Task A

2) Filter for Task Bs that have an early start before today plus x days, and apply an early start constraint on their current date

3) re-schedule

 

If Task Bs can never have their dates brought forward regardless of leadtime, then you must apply early start constraints to them all. NB: I have never come across such a situation.

Johannes Vandenberg
User offline. Last seen 2 weeks 3 days ago. Offline
Joined: 21 Jan 2010
Posts: 217

Hi Riz

I do not recommend to use constrained in this particular instance. I suggest using physical % completion for the duration of the activity you can play with % completion and remaining duration. In you example use 99 % complete but leave 3 days as remaining duration.

Regards Johannes