Predecessors and Succesors

[Nic]

I have Task A that is linked to task B. I need Task A to happen 3 weeks
before Task B starts. However, Task B is the main event and if Task B changes
and gets moved to the right 2 weeks I want all predecessors to automatically
move 2 weeks to the right as well....I have not been able to make this
successful..any tips

 

[Jim Aksel]

This is risky business as you are creating a task chain with no slack.
Here's one way to do it.

Place a deadline on the Main Event (this can be done from the task
information dialog box, advanced tab).

Make the Main Event constrtaint type "As Late As Possible". (Same tab). You
now have a task that will push its finish date all the way up to the Deadline
Date automatically. If they predict a late finish, then change the deadline
date to a date two weeks to the right.... Main Event automatically moves.
Schedule logic may have other predecessor chains that also drive the task to
the right.

For the predecessors you want to slip, make those of type "As Late As
Possible" as well. Now they will push. Keep in mind tasks with actual
progress will not move once the *Actual Start* field is popluated or you take
%Complete.

Here's an example of how we used this techique recently. An Electric
Utility is replacing electric meters on the houses in many cities. The main
drivers to the install are give ASAP constraint dates (things like
Manufacture and Test the Meter). They all run up to "Installl Meter in City
A" in the normal manner.

We also have a predecessor chain demanded by the local municipalities such
as "send a lette to the customer 30 days prior to meter install." This
letter meets the criteria you said and is given the ALAP constraint type with
a lag od 30 edays.y
There's another way to do it by using Negative Lag (called Lead Time) but
that is considered tacky and not a best practice. For example, I can
schedule Main Event using ASAP scheduling. I can then set "Mail Letters" as
Main Event FS-30ed so it will march the right when needed. Simple, to do.
However, this sort of begs the question that goes like this: "You mean, if I
want to guaranty Main Event happens, all I have to do is execute Task A 30
days prior?" In otherwordsm it assumes the certainty of a future event ...
as you said in your post, you already know that Main Event's start data is
not known with certainty.

Give them a try. Post back if you have more questions.
--
If this post was helpful, please consider rating it.

Jim Aksel, MVP

Check out my blog for more information:
http://www.msprojectblog.com

 

[Steve House]

A is in charge of B's timing, that's what "A is predecessor to B" means.
What could cause B to move? If A is B's predecessor, that means that the
timing of A's finish is what gives B permission to start, in your case at
least 3 weeks after A concludes. But that doesn't mean it WILL start on
that date, it could happen that the resource doing B gets hit by a truck on
the way to work that day and is laid up in the hospital so B's start will
have to wait until you hire a replacement. But as you are trying to set up
your schedule, B's delay means that weeks earlier, back before A began, you
should have anticipated the accident and delayed A accordingly. Such
clairvoyance is a very rare commodity.