Scheduling of activities with no duration

[Former Member]

Hello Forum, hello PS experts

I've created a network with app. 35 activities. I'm using the bottom-up scheduling scenario with forward scheduling. I'm using also activitites with no (0,0) duration as "milestones". So I have a lot of dependencies between real activitites and "milestones" as well as between two milestones. I'm not using a must start, only the earliest possible constraint. When I'm scheduling this network, I get two warnings (see fig. 1). When I'm now entering a duration for all "milestones" (activities w/o duration) the scheduling warnings don't appear anymore. Therefore I think that SAP has a problem with scheduling no-duration-activities. I also know about the different scheduling rules when a activity with no duration is involved:

Quoted SAP: "If an activity with no duration duration zero) falls on one of these times (midnight), the following special rules apply:
1) In forward scheduling, start and finish time are set to work finish or 24:00.

2) In backward scheduling, start and finish time are set to work start or 0:00.

But I'm not able to understand where this warning are coming from

I think that this warnings are connected with the following example: (see fig. 2)

- activity 1: must finish on 11.06.12 24:00 - duration: 5 days

- activity 2: no duration with a FS relationship to activity on:

After the scheduling the activity 2 is scheduled to the 11.06.12 24:00 . I think this behavior is okay

When I'm now changing the duration of the 1. activity to 0, the activity is scheduled to 12.06.12 00:00 (see fig. 3). And I think that this is the problem that causes me the warnings in my network.

Somebody has any ideas how to solve my problems, or why the second activity in the second scenario is scheduled differently?

many thanks for every informaiton I get

[Former Member]

hello

no help out there?

[Former Member]

Why you are not using real milestones instead of network activities as milestone?

regards,

Mahendra

[Former Member]

Hello

Because with activities I'm much more flexible. And I don't even say that we use them always as "milestones" as you could also say indicators. So we have the normal project planning and some important dates we add as 0-duration activities in the lower part of the planning as additional information. But nevertheless, we don't have a solution with the 0-duration activities

Best regards

[Former Member]

If I understood correctly..

The warning message for activities 0120 and 0350 while the activities with zero duration are 50 and 60.

The meaning of this message is that constraint(may be 'can not start before' or 'must start') which you have used is conflicting with the scheduled dates, as dates achieved after scheduling are before than 'must start' or 'can not start before', for those two (0120 and 0350) activities.

So system is showing the warning message 'constraint is too late'.

of course my understanding is based on screen shot you shared, you can show if activities 0120 and 0350 has any other constraint.

Regards,

Mahendra

[Former Member]

hey

I used a lot of activities without duration and I have not set any fixing constraint, but all activities are set with "earliest possible". And when I'm entering a duration, the warnings don't appear anymore.

what do you think of the fact of fig. 2 and 3?