In the Project System networks and projects are always scheduled forwards and backwards. The differences between the various scheduling types are the date from which the system starts scheduling and the direction in which it schedules first.
In forward scheduling the system:
1. Starts at the basic start date and schedules forwards
2. Determines the earliest activity dates
3. Determines the scheduled finish date
4. Schedules backwards
5. Determines the latest activity dates
6. Determines the latest start date
Similarly in backward scheduling the system:
1. Starts at the basic finish date and schedules backwards
2. Determines the latest activity dates
3. Determines the scheduled start date
4. Schedules forwards
5. Determines the earliest activity dates
6. Determines the earliest finish date
This means that in the Project System there are always two sets of dates for an activity, the earliest and the latest. The system settings determine how the dates of the WBS elements are determined and how these dates are passed on in the hierarchy depends.
For more information about scheduling, see Project System ® Dates in the SAP Library.
When a project is transferred from the Project System to Microsoft Project:
· If Schedule project from start was chosen in the OpenPS4MSP wizard, the earliest dates are transferred.
· If Schedule project from finish was chosen in the OpenPS4MSP wizard, the latest dates are transferred.
If a task with a constraint is transferred to the Project System, the same type of constraint is set in PS as in Microsoft Project. That means for example, if a start constraint is set in Microsoft Project a start constraint is also set in the Project System. This also applies to constraints that are set automatically by Microsoft Project.
When a project is transferred from PS to Microsoft Project, if a task has no predecessors, then the constraint of the task is set to Start No Earlier than if Schedule project from start was chosen in the OpenPS4MSP wizard during transfer; and to Finish no later thanif Schedule project from finish was chosen. This is to prevent Microsoft Project from changing the dates of the task during its scheduling.
In addition, it is possible for an activity to have two constraints (start and finish) in PS. However, tasks in Microsoft Project have only one constraint. Therefore, when downloading a project from PS to Microsoft Project, if Schedule from Start is selected, start constraints are used and if Schedule from Finish is selected, finish constraints are used.