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Mandatory or Early constraint...

Nicolas BergerMember for 20 years 4 months
Created
7
3
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Hi everyone,

I’d like to know practically for what reason we should use Mandatory Contraints ?
I have always used Early constraints...

My sub-contractor has given me a schedule (1000 activities)with a least 50 Mandatory constraints...how to consider this knowing that those milestones are not contractual ?

What should I suggest to my Subcontractor as comments ?

Thanks by advance

7 replies

Oldest first
  1. 0
    Nigel Winkley ·
    Nicolas

    A mandatory constraint is not as flexible as an early constraint. A mandatory constraint will affect the programme logic a lot more than an early constraint.

    If your contractor has used that many mandatory constraints it suggests that there is a problem with his logic and he is using the constraints to ’force’ the logic to work.

    If it was me, I would make a copy, remove a section of the constraints and re-schedule. See how far out his logic is.


    I generally use two mandatory constraints - Project Start and Project Finish and then only to force the float.

    Cheers

    Nige
  2. 0
    Nicolas Berger ·
    I Understand and I am agree !

    Thanks, I’ll check it out right now...
  3. 0
    Nigel Winkley ·
    Bon Chance
  4. 0
    Nicolas Berger ·
    So I removed all those "Mandatory constraints"...they all had predecessors...
    But result is, the sequence has changed and Finish date is 2 month earlier.

    And all those milestones are now spread out.
    This schedule must be rework...
  5. 0
    Paul Harris ·
    Nicolas

    I would like to clarify what a Mandatory constraint does to a P3 schedule.

    A Mandatory constraint stops float (negative or positive) calculating through the task with the mandatory constraint.

    A Mandatory constraint in the middle of a chain will break the chain and the float calculations will start again at the constraint. Normally this is not a good practice.

    Paul E Harris
    Eastwood Harris Pty Ltd, Melbourne, Australia
    Planning and Scheduling Training Manual & Book Publishers & Consulting
    www.eh.com.au
  6. 0
    Nigel Winkley ·
    Nicolas

    From your reply, it sounds like the contractor has ’forced’ his programme to meet the end date. Without the constraints, it finished earlier. This PROBABLY means that he has a lot of float that he is hiding - or making an allowance for lateness.

    Done similar things but not with mandatory constraints.

  7. 0
    Nicolas Berger ·
    Thanks Nigel !

    Actually it could mean that my sbucontractor is keeping some float in his pockets or maybe (and I think that’s the case) he’s a bit confused in his sequence of scheduling.

    Thanks anyway guys for your participation !

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