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Calendar for Scheduling Relationships lag

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Abbas Rajabpour
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Hi everyone,

 

There is an option to choose between four different calendars for this one, can anyone tell me the difference and which one is better and why?

If there is any link to go thru that will work as well.

Rafael Davila
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By the same token individual links may have different probabilistic lag parameter values.

2022-11-19-06-24-27

Santosh Bhat
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Rodel, in the context of a discussion about P6, a "project" is the individual project (or schedule/file if you want to call it something else). P6 only applies the relationship calendar setting to all relationships in a project.

If your project/portfolio/program contains multiple schedules combined together, then thats not a single project in P6.

 

Below is example from Safran Project, you can set the calendar relationship calendar per link, use different duration units fro the link and even set the lag value to be as a %.

Rafael Davila
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Individual calendar links are a basic feature in Spider Project, more advanced features are volume of work lag and double dependencies with lags.

2022-11-17-04-56-52

Rodel Marasigan
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Hi Santosh,

Yeah...right. You said entire project which means the whole projects (main project and sub projects). I have not encounter a planning software that define relationship lag calendar per relationship. Can you name one?

Santosh Bhat
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Rodel, you mis-interpreted what I wrote. P6 applies the setting to ALL relationships in the project. Other tools let you specify the setting PER RELATIONSHIP.

Rodel Marasigan
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Hi Abbas,

It all depends on the project requirement such as:

If using only one calendar : Lags using Predecessor or Successor calendar will be no difference.

If you are using multiple calendar and you have different start hour and different finish hours, use 24 hour and make sure you are aware that this lag is continues 24 hours work period. If multiple calendar with same start but different finish hours, use predecessor calendar. If multifple calendar with different start with same finish hours, use successor calendar. Be carefull as if not properly use you may end up negative float even the project is not yet started.

Abbas Rajabpour
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Hi Rodel

Thanks for your reply,

Could you be more specific what you would do?

Rodel Marasigan
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Hi Santosh,

I agree with you that project has different preference and you can select which is the best options in accordance to project requirement.

But I don't agree on this statement "What I will say is that it sucks that P6 applies this across the entire project, other scheduling tools will let you set this per relationship, which is actually a better way of doing it!". P6 does not applies this across the entire project. Yes the default is "Predecessor Activity Calendar" which can be change anytime when running the schedule. The Project retain the setting selection and will not change on other project. You can see it from the Log.

Santosh Bhat
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David, your method is the better option for your projects that use multiple calendars, which I see as only proving my definition that each project has its own requirements.

The real issue with lags, regardless of the calendar being used, is that lags and how they affect activity paths can be quite hard to ascertain withouth diving into the details. There is a whole lot of improvements to relationship handling and some tools already enable them, whereas other don't. For example:

  • Setting lags as % values of an activity's duration
  • Setting lags as X units (or %) befor the end of an activity
  • Coding of relationships

That last one is the one that I think would be the most interested. It could in theory allow you to code and flag relationhsips and have the model caluclated based on the, For example flagging a relationship as a resource link, to run the shcedule with har dcoded resourcing on/off.

Abbas Rajabpour
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Hi David, based on your explanation, I found it more realistic to use the one with 24 hour calendar. Just a quick question, if the calendar for the predecessor is 2 days in a week and only on Tuesdays and Thursdays, that 120 hours of lag means, to use 2 weeks and a half to push the successor activitty, Am I right? So what is the difference between this one and the way we just put 5 days of lag and use the predecessor calendar? Doesn't it push the successor the same?
david kelly
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I disagree with Santos! Diary entry, everyone

 Best practice, and essential on projects with multiple calendars,  is to always use 24hour, and always enter lags in hours. E.g. if the lag is 5 days, enter 120h into the lag dialogue. This way, no changes in any calendar will change the wall-clock time of any lag.

Santosh Bhat
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Hi Abbas,

 

The four options are essentially how you want the duration of the lag to be calculated. So that when you put a lag in of 1 day, how do you want that 1day to be determined. The default, or most widely used option is that any lag uses the Preceeding activity calendar to determine the lag. 

There is no such thing as the "Better option" as it all depends on the specific type of project you are planning. What I will say is that it sucks that P6 applies this across the entire project, other scheduling tools will let you set this per relationship, which is actually a better way of doing it!