AUowlnl’ for Task Delays and Overlaps Project Management Help

Even though two tasks may be linked, the planned start or finish date of a task may be dependent on a number of other factors. In a finlsh-to-start relationship, finishing a predecessor task doesn’t necessarily mean that you can start the successor taskimmedtately.
If you’ve ever flown on a commercial airline, you have probably experienced this firsthand.

Airlines routinely include lag time, a delay between landing and taking off again, in their schedules. This allows time for deboarding, refueling, exchanging baggage, restocking the kitchen, cleaning the cabin, and reboarding. Lag time is defined as a delay between any two dependent tasks.

In Figure 8.19, tasks 15 and 16 provide an example of lag time. In this example, the marketing team is planning to request business directories for the local community and then use those materials to identify major competitors. Although the task of requesting directories should take only two days, it may take a few additional days for all of the directories to arrive. By building in a five-day lag time, you can more accurately reflect the expected lag time between requesting the directories and beginning the process of identifying competitors.

On the other hand, if a successor task can start before its predecessor is finished, this can be demonstrated through the use of lead time. Lead time, then, is the overlap between dependent tasks. Let’s say, for example, that one task is to identify target clients’ of the new regional sales office. Based on the results of this process, the marketing team plans to create marketing materials.

As long as you allow some lead time to establish a general sense of the target clients, the marketing team can begin drafting marketing materials. Tasks 18 and 19 in Figure 8.19 show this relationship.

Entering Lags and Lead Time

Lag time and lead time are both entered in the Lag field or in the Predecessors field. Lag time is entered as a positive number and lead time as a negative number. Lag time and lead time can also be entered as a percentage of the predecessor’s duration.

A 40 percent lead time, for example, means that the successor task would start when the predecessor is 60 percent completed. Use a percentage when you want the lag or lead time to increase or decrease proportionately if the duration changes .

You can enter lag time and lead time by using the Task Information dialog box, using Task Form view, using the Task Entry table, and using the Task Dependency dialog box. To use the Task Information form, follow these steps:
1. Double-click a task to open the Task Information dialog box.
2. Click the Predecessors tab.
3. Select the Lag field.
4. Enter a number or percentage in the cell, or use the spin arrows to increase or decrease the lag or lead time.
S. Click OK to close the Task Information form. To use Task form view, follow these steps:
1. Click Window >- Split in Gantt Chart view to open the Task form.
2. If Predecessors are not visible, right-click on the Task form and choose Resources & Predecessors, Resources & Successors, or Predecessors & Successors.

3. Select the Lag field.
4. Enter a number or percentage in the cell, or use the spin arrows to increase or decrease the lag or lead time.
S. Click OK on the Task form torecord the changes. To use the Task Entry table, follow these steps:
1. Drag the vertical split bar to the right to display the Predecessors field.

2. Select the field, and edit the predecessor to include the lag or lead time information. You must also enter the abbreviation for the relationship type, if it is not already present. Figure 8.20 shows one example of five days of lag time (lSFS+S days) and one example of 40 percent lead time (18FS-40%).

To use the Task Dependency dialog box, follow these steps: 1. Double-click the connecting line linking two tasks in the Gantt Chart to open the Task Dependency dialog box.

2. Select the Lag field.

3. Enter a number or percentage in the cell, or use the spin arrows to increase or decrease the lag or lead time.

4. Click OK to close the dialog box and save the changes.

As you are planning a project, you may discover that a task will start on particular date, but the person completing the task is going on vacation two weeks into a fourweek task. Rather than waiting until she is back at work to start the task, you can split the task so that part of it is completed before she goes on vacation and part of it after.

Whether the interruption is planned or comes up unexpectedly as the project is  underway, you can split a task to show the interruption in task completion. To split a task, follow these steps:
1. In Gantt Chart view, click the Split Task button on the Standard toolbar or choose Edit >- Split Task from the menu. The Split Task Information box opens and the pointer changes shape, as shown in Figure 8.21. 2. Position the pointer over the task you want to split. As you move the pointer, the Split Task Information task shows you the start date the pointer is over. 3. When you locate the correct date, click the task bar to split the task. Project splits the tasks, separating the two sections by a day. Figure 8.22 shows the split task. 4. You can split a task into as many sections as you want. Repeat Steps 1-3 to split the task into further sections. After you split a task, you can drag tho split section to the desired restart date. Point to the split section and drag with the four-headed arrow pointer. As you start to drag, thepolnter changes shape once again to become a two-headed arrow, and the Task Split Information box reopens. Figure 8.23 shows the process of changing the start date of a split section.

Changing the Duration of a Split Task

To change the duration of a split task, point to the right side of any task segment. The pointer changes shape to a vertical line with a right arrow. Drag the end of the segment to the new end date, as shown in Figure 8.24. To lengthen a task’s duration drag to the right. Drag to the left to shorten it.

Constraining Tasks

When you create a project, you can schedule the project to start on a specified date or to finish on a specific date. When you set a project start date, tasks are scheduled to start as soon as possible. When you set a project finish date, tasks are scheduled to start
as late as possible. The “as possible” is determined by the relationships (links) that you establish between tasks. As soon or as late as possible is directly related to the start or finish date of a predecessor task.

Other factors, however, may constrain the actual start or finish date of a particular task. For example, if one of the project’s tasks is to meet with an individual to review the project and that person is going to be out of town for the period of time you want to meet, the project’s schedule can be negatively affected. You can account for this and other scheduling problems by assigning a constraint to the task.

Understanding Constraint Types

In Project, you can choose from eight different constraint options. Table 8.1 describes these options.

Applying Constraints

To apply a constraint to a task, follow these steps:
1. Click the Task Information button on the Standard toolbar, or double-click a task to open the Task Informatidn dialog box.

2. Click the Advanced tab.
3. Click the drop-down arrow to open the Constraint type list.
4. Choose the desired constraint from the list.
S. Open the drop-down list in the Constraint Date field to select a date for the constraint (AsSoon As Possible and As Late As Possible do not need a Constraint Date).
6. Click OK. Flexible versus Inflexible Constraints
Inflexible constraints are constraints that restrict scheduling because they require that a task start or finish within specific parameters. Flexible constraints allow Project to calculate the schedule to making appropriate adjustments based on the constraints applied. Table 8.2 shows a list of inflexible and flexible constraints, depending on whether the project is scheduled from the start date or the finish date. When applying constraints, apply inflexible constrairraomy when they are absolutely necessary. When you apply inflexible constraints, you are restricting Project from establishing a schedule for all the tasks that is consistent with the durations and other scheduling parameters ¥.ou have assigned to tasks. If, for example, you apply an inflexible constraint to a task, it may be impossible to complete the predecessor or successor tasks
within the constraint. If this occurs, Project displays the Planning Wizard message, shown in Figure 8.25, and asks you how you want to handle the contlict.Select Cancel to remove the constraint and avoid the ;Lheduling conflict, or select Continue to save the constraint and allow the scheduling conflict.

Reviewing Constraints

Project indicates that a constraint is applied to a task by adding an Indicators icon to the Indicators field in the Entry table. A blue square on the right side of the calendar icon indicates a flexible task constraint. A red square on the left side indicates an inflexible task constraint. Point to the Constraint indicator to determine what kind of constraint is applied.

Removing Constraints

You can remove a constraint by applying an As Soon as Possible constraint to a task in a project scheduled from the start date or As Late as Possible to a task in a project scheduled from the finish date.

To remove constraints on more than one task, follow these steps:
1. Select the tasks in the Task Entry table by dragging to select successive tasks or by holding Ctrl and clicking to select nonconsecutive tasks.
2. Click the Task Information button on.the Standard toolbar or choose Project > Task Information from the menu. The Multiple Task Information dialog box opens;
3. Click the Advanced tab.
4. Click the drop-down arrow to open the Constraint type list.
S. Choose As Soon As Possible in a project scheduled from the start date, or choose As Late as Possible\ in a project scheduled from the finish date.
6. Click OK to save the new constraint types.

WARNING Any information you change in the Multiple Task Information dialog bolt affects all the selected tasks, so be careful to only change things that you want reflected in each of the selected tasks.

Resolving Constraint Conflicts

Constraint conflicts arise when you apply constraints that are in conflict with other parts of the schedule. For example, if you apply a Start No Later Than constraint to a task, such as Order Furniture, and specify a date that actually precedes the finish date of the predecessor, Assign Offices, Project cannot resolve the conflict. You must decide whether the constraint is necessary or whether there is some other way to schedule the tasks to avoid the conflict.
Ask the following questions to d

•etermine how to resolve the conflict:

• Is the constraint really- necessary? Was the constraint applied jntentlonally or accidentally? What would have to change in the project plan, for it to be possible to remove the constraint?
• Can the finish date of the predecessor task be changed so that it is actually completed by the constraint date?
• Can the duration of the predecessor task be changed so that It can be com-. pleted by the constraint date? This may involve having to assign additional resources to the task. For more about using resources to resolve conflicts, see 9.
• Is it possible to unlink the tasks that are In conflict? Perhaps the task with the constraint would be better linked to a different task or not linked to any task.
• Can the constraint be changed from an inflexible constraint to a flexible one? For example, could the restraint be changed from a Must Start On to a Start No Earlier Than constraint? Not Honoring Constraint Dates Another way to resolve constraints is simply to not honor them in the schedule.

Project has an option that is turned on by default to always honor constraint dates. You can turn this option off by following these steps:
1. Choose Tools >- Options and clicking the Schedule tab.
2. Clear the Tasks Wilt Always Honor Their Constraint Dates checkbox.
3. Click OK to save the new settings. When this option is turned off, Project notes the conflicts, but continues to calculate the schedule as if the conflicting constraint weren’t applied. Figure 8.26 shows
the icon and message that Project displays when a constraint is not being honored.

Setting a Deadline Rather than setting an inflexible constraint, which might negatively affect scheduling, you can now record a deadline date in Project 2000. A deadline is the date you want or need a task to be completed. Setting a deadline does not affect the task sc~edule in any way. However, if the deadline passes and the task is not completed Project displays an indicator in the Indicator column. Project notes a deadline in the Gantt Chart with a downward-pointing arrow.

Posted on November 26, 2015 in Scheduling And Linking Project Tasks

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