(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?
(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.
Here's how to investigate and report lag assignments in an entire Primavera P6 schedule http://ow.ly/iVSk303VXmw
Printer-friendly version
Send to friend
in p6 under schedule (F9) then options at the bottom there is an option for which calendar that you want to use to calculating the relationship lag. This is project specific NOT activity specific.
Lag calendars exist for one reason, otherwise there would only exist 24/7 lag calendar. That your software is poor at handling it is another issue. To say a single calendar will take care of everything is in error.
If you set your lag to 24h/7dw then no lag will consider calendar exceptions.
More frequently than not these calendar exceptions must be considered as to keep the distance between the linked activities. Because the distance is usually defined by some required progress on predecessor activity it shall usually be based on the predecessor calendar. It is ok to define default lag calendar to be defined by predecessor calendar but not allowing for individual calendar assignment when needed is not good.
For software that cannot give you necessary control on lag calendar some schedulers suggest using the default everyone expects, if this is not what it should be then use an activity to represent the lag with the calendar you need.
Even some Risk Analysis software incapable of modeling probabilistic lag go as far as suggesting to use activities to model probabilistic lag.
Zahid,
You might use this in any number of situations when your tasks don't follow one another end to end.
Let's make it generic, if the concrete, trench and pipe thing is confusing:
| Date -> | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Task 1 | - | - | |||||
| Task 2 | - | - | - | ||||
| Task 3 | - | - | - | - |
If your Gantt chart has 3 tasks. Task 1 and 2 follow one another as you might usually expect:
Rob does Task 1. Once he is finished, he moves to Task 2.
Tasks 2 and 3 don't run end-to-end they overlap! a normal "Finish to Start" relationship here isn't right. We need a "Start-to-Start" and... a Lag!
Why do we need a Lag?
Well if we use a Start-to-Start for Tasks 2 and 3, then both tasks will start on 3rd date. We need to introduce a lag of 1 day, so that Task 3 can begin a day later, on 4th.
When would I need to use that?
We're back to the concrete I'm afraid!
Rob has been pouring concrete to his heart's content and behind him, Jane has been getting ready to lay some bricks.
Rob has finished pouring in one part of the site. Can Jane begin immediately?
No Way!
Jane would ruin Rob's work. Poor Rob.
Much better if we give Jane a programme that says: "Jane, you have to wait a day for this concrete to set".
Now Rob is much happier, because his concrete is safe and sound whilst Jane uses her time wisely elsewhere for a day.
Does that make sense?
Phil
....... But which calendar to use to count the lag?
Suppose we are pouring concrete in a project where the activity calendar is eight hours a day, five days a week. We need two days for the concrete to cure before we can start the successor activity, and by chance the concrete pour finishes at 17:00hrs on Friday.
The concrete will cure on Saturday and Sunday - but the default in P6 is the predecessor calendar, so the successor activity starts on Wednesday.
In scheduling options, I always chose the "Calendar for relationship Lag" option as 24h. Then when I am entering the lag on an activity I always quote it in hours e.g. a five day lag I enter as 120h, even if the durations are shown in days. This means I get a lag of exacty five "wall clock" days no matter how many and how complex the project's calendars......
As I mentioned in my example of 'concrete curing', many folks use this to more acurately model realtiy in the schedule. The better job we do of this, hopefully will reduce surprises as the project progresses.
Yes I Understood that. Thanks !
But my question was, Yes i am gettting the information that, Lag is there for "A" activity of "5" days lag. But what is the use of me knowing that. How do I use this to my Advantage if i am a Contractor or PMC?
A common example of lag is the lag time for the curing of concrete. In this example lag modifies the finish to start (FS) relationship between the ‘pour concrete floor’ activity and ‘install wall frame’ activity. After you pour the concrete you need to wait a period of time for the concrete to cure before you can begin installing wall framing on the concrete floor. This waiting time between ‘pour concrete floor’ and ‘install wall frame’ is your lag time.
Another example of lag is the lag that modifies the start to start (SS) relationship between ‘dig trench’ and ‘lay pipe’ in trench. In this example lag models the time between the start of ‘dig trench’ and the start of ‘lay pipe’. After you begin digging the trench you must continue digging the trench, say 3-days, before you have enough room in the trench to being laying pipe in the trench. The time between the start of ‘dig trench’ and start of ‘lay pipe’ is your lag time.
I hope this helps!
But how to make use of this ? Where and When is it Needed ?
Email: PPadmin@planningplanet.com
Replies