Overview
A rescheduling plan is an explicit modification of the project plan by the project manager in real-time. Rescheduled task changes are visible immediately to the Project Manager for evaluation.
- The task efforts are based on the Planned Start and Planned End dates of the tasks.
- The Resource assignment for the task is dependent on the planned Start and End dates and is not effort-driven. Resource calendar will not be considered while re-scheduling tasks.
- The working days, non-working days, and exceptions of the project calendar will be taken into consideration during the re-scheduling of the task plan if no resources are assigned to the task.
- Only Finish-To-Start (FS) task dependency type is supported.
‘Re-scheduling’ logic embedded in Simple Scheduling task planning is explained with help of the following scenarios.
Scenario 1: Reschedule a task when there are No Actuals and No Resources assigned to the task
Tasks that have no Actuals or Resources assigned to them, can be rescheduled to ‘New Planned Start Date’ and ‘New Planned End Date’ by adding or modifying task dependencies with a lag or a lead.
The existing tasks are rescheduled to the new dates based on dependency with other tasks and also after considering the number of working/non-working days from the project calendar.
Example:
There are two dependent tasks T1 and T2 in a project.
To calculate the duration of the task for T1, calculate the total number of days of the task and deduct the number of non-working days and add to it the exception working days. The resultant number of days will be the duration of the task.
In the case of T2, the duration of the task will be the difference – in the number of days – between the planned end date and planned start date, as there are no non-working days and exception working days.
Due to changes in the project plan, T1 – with a task duration of 5 days – is rescheduled to ‘New Planned Start Date’. The ‘New Planned End Date’ of T1 will now include the two nonworking days of the week.
The ‘New Planned Start Date’ of T2 being dependent on the ‘New Planned End Date’ of T1 will also be rescheduled and will now include the two non-working days.
In both the above scenarios, the task duration remains the same as prior to rescheduling. Only the ‘Planned Start Date’ and ‘Planned Finish Date’ are changed.
Scenario 2: Reschedule a task when the Resource is assigned to the task for the entire duration of the task – Also, the task has no Actuals
The tasks that have no Actuals but do have a resource assigned to them for the entire duration of the task can be rescheduled to a ‘New Planned Start Date’ and ‘New Planned End Date’. Here the Resource assignment is for the entire duration of the task. In such scenarios when the task is rescheduled, the assigned resources to are rescheduled based on the rescheduled dates of the task.
The ‘New Planned Start Date’ and the ‘New Planned End Date’ of the tasks are derived using the same logic as explained in Scenario 1. The following example will explain how new dates of resource assignments are derived.
Example:
There is task T1 in the project starting on 9-Jun-08 and ending on 13-Jun-08. The duration of a task, in this case, is 5 days. There is a resource assigned to this task with the same period as that of task T1.
When T1 is rescheduled to a new planned start date, the resource assignment also gets rescheduled because the Start date and the End date of the resource (Planned and New Planned) are similar to that of the task.
Scenario 3: Reschedule a task when the Resource is assigned to the task for a partial duration of the task – and the task has no Actuals
It is a common scenario with projects where the resources are partially assigned to various tasks in a project. In such cases, while rescheduling tasks, the resource assignment duration is not affected, i.e. the number of days the resource is assigned to the task is not changed. What changes in the date of the assignments? While rescheduling tasks and resource assignments, it will consider the number of working days and the number of non-working days based on the project calendar.
To reschedule the tasks that have partially assigned resources, the ‘New Planned Start Date’ and the ‘New Planned End Date’ are changed – either moved ahead or moved back on the time scale as explained in Scenario 1. The following example will explain how new dates of resource assignments are derived.
Example:
Task T1 in a project starts on 4-Aug-13 and ends on 8-Aug-13. This task is for 5 days and a resource, R1, is assigned from 6-Aug-13 to 7-Aug-13. This is the partial assignment of the resource, meaning there is a slack which is the difference in days between the planned start date of resource assignment and that of the planned start date of the task.
While rescheduling the task, the following factors are considered:
- New Planned Start and End Dates of the Task
- Duration of resource assignment
- New Planned Start and End Dates of Resource Assignment
Based on this data the task is rescheduled to new planned dates (Start and End) and the resource assignment that is associated with the task also gets rescheduled accordingly.
Scenario 4: Reschedule a task with multiple predecessors – Task has no Actuals
When a particular task is dependent on one or more predecessors, then the rescheduling of one of the predecessors will affect the scheduling of the dependent task.
The dependencies could be spanned at different time frames, and the dependant task would be starting at a different time frame, then when one of the preceding tasks gets rescheduled – moved back or moved ahead in the time frame – then the dependant task will also get moved back or ahead in a time frame.
Consider the example,
There are 3 tasks T1, T2, and T3, of which T1 has a lead of 4 days over T3 and the Task Duration of T1 and T2 is respectively 3 days and 2 days. Task T3 is reliant on both Tasks T1 and T2. So when T1 is rescheduled to a New Planned Start and End Dates, Task T3 also gets rescheduled, keeping in mind the lead of 4 days of T1. In case there are non-working days appearing in the new duration of task T3, they will not be calculated but will be indicated in the Gantt view of the tasks.
Scenario 5: Reschedule a task with Actuals
Tasks that have Actuals filed against it cannot be rescheduled i.e. such tasks are ignored while rescheduling.
In a scenario of a particular task’s scheduling, when there are predecessor tasks, and one of the predecessor tasks has Actuals; the task with Actual is not considered while calculating the New Planned Start Date and New Planned End Date of the scheduled task.
Example:
Tasks T1, T2, and T3 are defined as they are reliant on one another; T2 is dependent on T1 and T3 is dependent on T2. Also Task T2 as Actuals filed against it, which means that this task will not be considered for rescheduling. Similarly, tasks that are dependent on this task will also not be affected by the rescheduling of the predecessor tasks.
So when T1 is rescheduled to a New Planned Start and End Date T2 and T3 remain unaffected because T2 contains Actuals and T3 is dependent on T2.
Scenario 6: Reschedule ‘Closed’ Task
While rescheduling a task, if there happens to be a closed task, then that task is not considered while calculating the New Planned Start Date and New Planned End Date of the scheduled task.
Tasks that are marked ‘Complete’ (Overall Status = Closed) will not be modified (rescheduled) i.e. such tasks are ignored while rescheduling.
Example:
Out of tasks T1, T2, T3 – T2 is a closed task and hence will not be considered for rescheduling. Task T3 is dependent on task T2 because T2 is a closed task and is not affected by the rescheduling of Task T1. T3 too will be unaffected by rescheduling.
While rescheduling, Tasks T2 and T3 remain unaffected.
Scenario 7: Reschedule Summary Task
A summary task is the roll-up of the data from all the child tasks. The ‘Planned Start Date’ of a Summary Task is the Minimum of the ‘Planned Start Date’ of all child tasks. The ‘Planned Finish Date’ of the Summary Task is a Maximum of the ‘Planned Finish Date’ of all child tasks. Also, the summary task does not have dependencies.
Example:
There are two tasks T1 and T2 with task duration of 5 days and 6 days respectively. In this case, the summary is the roll-up of both the tasks, i.e. 8 days, and NOT the sum of the two tasks. (11 days)
When T2 is rescheduled and its duration changes from 6 days to 10 days, the Summary task too changes automatically from 8 days to 12 days.
Scenario 8: Reschedule Milestone Task
The Milestone task takes its Planned Start Date and Planned End Date from the predecessor task. (Refer to Scenario 1 for details). So when a task plan having a Milestone task is rescheduled then the Milestone task will take the ‘New Planned End Date’ of the predecessor’s task as its ‘New Planned Start Date’ as well ‘New Planned End Date’.
Scenario 9: ‘Planned End Date’ of the Project
The Project End Date will get updated if any of the project tasks ‘Planned Finish Date’ is greater than the ‘Planned End Date’ of the project.
If the MAXIMUM of the ‘Planned Finish Date’ of the Tasks is more than the ‘Planned End Date’ of the project then, the Project End date will be set to the MAXIMUM of the Planned Finish Date of all tasks.
If the MAXIMUM of the Planned Finish Date of the Tasks is less than the Planned End Date of the project then, the Project End date will not be modified.