Chapter 11 - Shortening Your ScheduleIntroduction Critical Tasks: The Tasks That Make a Difference Identify Tasks on the Critical Path Sort Critical Tasks by Duration Determine the Tru
Trang 1Chapter 11 - Shortening Your Schedule
Introduction
Critical Tasks: The Tasks That Make a Difference
Identify Tasks on the Critical Path
Sort Critical Tasks by Duration
Determine the True Length of a Schedule with Slipped Tasks and Inflexible Constraints Strategies for Cutting the Project Scope
Delete Critical Tasks
Cut the Scope of a Task
Strategies for Reducing Task Duration
Assign More Resources
Increase Working Hours
Assign Overtime Work
Strategies for Starting Tasks Earlier
Change the Task Sequence
Break a Large Task into Smaller Tasks
Add Lead Time to Tasks
Change the Link Type
Change the Constraint Type
Change the Task Type
Fixed-Units Tasks
Fixed-Work Tasks
Fixed-Duration Tasks
Trang 2In many projects, time is the main constraining factor: the project deadline must be met That may mean you need to finish a project sooner than the end date on your project schedule If you’re hemmed in by time
limitations, your best solution is to shorten your schedule
You can shorten your schedule in three major ways:
• Reduce the duration of individual tasks
• Cut the project scope, which means removing tasks
• Reschedule tasks to start earlier than originally scheduled
You can use any or all of these methods to shorten your schedule By combining all three methods, you can make the biggest impact on your schedule Depending on your particular circumstances, you might be restricted
to using only one or two For instance, you might not be able to cut the project scope
Critical Tasks: The Tasks That Make a Difference
When you want to shorten your project schedule, where do you begin? You begin by examining your project’s
critical tasks, the tasks that must finish on time for the entire project to finish on time The project plan’s critical path is the sequence of tasks that ends on the latest finish date The finish date of the last task in the critical
path is the project finish date
Trang 3By default, a critical task has zero total slack time, which is the amount of time a task can slip before it delays
the project finish date If any critical task slips, the project finish date will likely slip as well
Critical tasks are like stacked sections of a column holding up a roof The column is the critical path, and the roof represents the project finish date Noncritical tasks are like decorative columns that are lower than the roof To raise or lower the roof, you adjust the height of the "critical" column
If you increase the height of a column of noncritical tasks so that the roof rests on it instead, then that column becomes "critical." The original column of critical tasks becomes "noncritical."
Trang 4Microsoft Project recalculates the critical path every time you change task data A critical task may become noncritical and a noncritical task may become critical as you assign resources,
change links, and so on
You can experiment with your project plan by altering one critical task at a
time Change one element of a critical task to see how the change affects the
schedule as a whole For example, you can reduce a task’s duration to see if
that change causes the project to end sooner Or, if a resource assigned to
work on two concurrent tasks becomes overworked, you can reschedule one of those tasks
But don’t start altering critical tasks to fine-tune your schedule until you can distinguish critical tasks from noncritical ones Microsoft Project provides several ways for you to display critical tasks and focus on the ones to which you should give the most attention
Identify Tasks on the Critical Path
Because critical tasks play such a key role in determining the project length and finish date, Microsoft Project provides two views that visually distinguish critical tasks from noncritical tasks To enable you to zero in on critical tasks, both the Detail Gantt view and the Tracking Gantt view display critical tasks in red
To identify tasks on the critical path
1 On the View Bar, click More Views
2 In the Views list, click Detail Gantt or Tracking Gantt, and then click Apply
When you display both critical tasks and noncritical tasks, you can see how altering critical tasks affects both the project end date and noncritical task dates If a noncritical task becomes critical, you may need to alter it to modify its effect on the project end date
Sort Critical Tasks by Duration
Because critical tasks are the ones that affect project length, the longest critical tasks have the biggest effect When it’s important to maintain or shorten the project length, you’ll want to focus first on shortening the critical tasks with the longest duration You can do this most easily by sorting critical tasks by duration
To sort critical tasks by duration
1 On the View Bar, click Gantt Chart
2 On the Project menu, point to Filtered for, and then click Critical
3 On the Project menu, point to Sort, and then click Sort by
4 In the Sort by box, click Duration, and then click Descending
5 Click Sort
Determine the True Length of a Schedule with
Slipped Tasks and Inflexible Constraints
Decreasing the duration of a noncritical task has no effect on the project end date
Trang 5As you track progress by entering actual start and finish dates for tasks, you may find that the project finish date remains the same, even when a number of tasks have been completed later or have taken longer than originally planned The reason could be that one or more tasks in your schedule have an inflexible constraint (Must Start
On, Must Finish On, Start No Later Than, Finish No Later Than) applied
A task with an inflexible constraint doesn’t move, even if predecessor tasks finish later than planned A task with
a Must Start On constraint, for example, doesn’t get "pushed" to a later start date if tasks that precede it finish later than their original finish dates Instead, it remains firmly anchored to its specified start date while
predecessor tasks move
The tasks that follow the inflexible task remain unaffected by the late-starting tasks Therefore, even though tasks that precede the inflexible task are late, and the project as a whole is late, Microsoft Project may show your schedule incorrectly on the original project finish date Because of the task with the Must Start On constraint, Microsoft Project can’t recalculate a more realistic project finish date
What do you do if you want to know the "real" project finish date? You can allow the inflexible task to move without removing its Must Start On constraint You can choose to make schedule changes override constraints
By default, Microsoft Project honors constraint dates The start and finish dates of a linked task with an inflexible constraint, such as Must Start On, stay the same even if the schedule changes If you want Microsoft Project to automatically recalculate a constrained task’s start and finish dates when the schedule changes, you can choose
to have schedule changes override constraint dates Because tasks with flexible constraints such as As Soon As Possible and As Late As Possible have no fixed dates to honor, they behave the same way regardless of the option you choose
When you use constraints in your project plan, you can choose to have schedule changes override constraints or have constraints override schedule changes — for all affected tasks A project plan cannot accommodate both options at the same time
To set constraints so schedule changes can override them
1 On the Tools menu, click Options
2 Click the Schedule tab
3 Clear the Tasks will always honor their constraint dates check box
Strategies for Cutting the Project Scope
No change can affect your project as much as cutting its scope, an action that produces a cascade of benefits In one stroke, you can shorten the project duration, reduce the number of required resources, and slash costs The most obvious way to cut the scope is to remove critical tasks For example, if a software developer can’t complete all the planned features of a new software program by the deadline, he or she can cut some of the
Trang 6features, and thus the tasks required to implement those features This can also be the most difficult method, because you must first identify the tasks that are not absolutely necessary for completing the project
Another way to cut the project scope is to reduce the scope of individual tasks A task’s scope consists of the specific task goal and the amount of time and effort required to achieve it By reducing a task’s scope, you may reduce the overall time, effort, and cost required to complete your project
Delete Critical Tasks
You can delete critical tasks that aren’t absolutely required to meet your project goals When you delete critical tasks, you will probably see an immediate effect: the project ends earlier In addition, you may free up resources that you can assign to more urgent tasks in your project or to other projects
When you delete a task that is linked to both its predecessor and successor tasks with finish-to-start (FS) links, Microsoft Project automatically links its predecessor task to its successor task with an FS link (by default) If you delete a task with any other type of link, you need to link its predecessor to its successor manually after you delete the task
To delete a critical task
1 On the View Bar, click Gantt Chart
2 In the Task Name field, select the task you want to delete
3 On the Edit menu, click Delete Task
Cut the Scope of a Task
As you examine your schedule, you may find that some critical tasks accomplish more than they need to, and therefore take longer than necessary For example, if hanging clocks for an exhibit is a critical task, you can reduce its scope by hanging fewer clocks than originally planned When you decide to cut a task’s scope, you show this in your project plan by decreasing the task’s duration Shortening the duration of a critical task can shorten the project duration
To decrease the duration of a task
1 On the View Bar, click Gantt Chart
2 On the View menu, point to Table, and then click Entry
3 In the Duration field, enter a new duration for the task
4 Click or press ENTER
Strategies for Reducing Task Duration
Trang 7No matter how many times you look through your project plan for ways to cut the scope and eliminate tasks, sometimes you can’t find any You may conclude that all of your project goals are essential and every task in your plan is needed to meet those goals But that conclusion doesn’t help you do what you must — shorten the schedule
When you’ve determined that the scope is just right and you can’t eliminate
any more tasks, you can shorten the schedule by reducing the durations of
critical tasks Use the following methods to reduce the durations of critical
tasks:
• Assign more resources to tasks Use this method if you have extra resources or underused resources
• Increase the working hours for one or more resources Use this method if you can increase the working hours for the resources
• Assign overtime work Use this method if resources with the required skills are already fully utilized during their normal working hours and if the budget permits the increased cost
Assign More Resources
If extra or underused resources are available, you can keep cost increases to a minimum while reducing task duration By assigning additional resources who have available hours during their normal working days, you can pay them at their standard rates, which is less costly than paying overtime to already assigned resources You may already have part-time resources on your team, or you may be able to shift some resources from noncritical tasks to critical tasks You could also hire new resources If additional units of the same resource are available, you can increase the number of resource units assigned to a task For example, if the three painters assigned to paint a wall can’t finish the job soon enough and a fourth painter is available, you can assign the fourth painter to the task For information about resource units, see Chapter 8, "Assigning Resources to Tasks."
To assign more resources to a task
1 On the View Bar, click Gantt Chart
2 In the Task Name field, select the task for which you want to assign more resources
3 Click Assign Resources
4 In the Name field, select the resource you want to assign to the task
o To assign a single resource, enter a number in the Units field to indicate the percentage of
working time you want the resource to spend on the task To assign the resource full-time, enter 100%; for part- time, enter a smaller percentage
o To assign several different resources, hold down CTRL, and then select the resources
o To assign more than one resource from the same set of resources, enter the number of units in
the Units field For example, if you assign two painters from the Painters set, enter 200%
Sort tasks by duration to see which critical tasks to shorten first
Trang 8If necessary, type the name of a new resource in the Name field
5 Click Assign
A check mark to the left of the Name field indicates that the resource is assigned to the selected task
To increase the resource units assigned to a task
1 On the View Bar, click Gantt Chart
2 In the Task Name field, select the task for which you want to increase resource units
3 Click Assign Resources
4 In the Units field for the resource, enter the number of resource units you want, and then click Assign Increase Working Hours
Sometimes you just can’t get additional resources for the tasks you want to shorten One way to handle this situation is to reduce the durations of those tasks by increasing the number of working hours for the resources already assigned Increase the number of available hours for a resource by increasing the resource’s working hours on his or her resource calendar
Microsoft Project calculates a task’s duration based in part on the working hours of assigned resources For example, a painter with a 6-hour working day is assigned full-time to paint gallery walls, a task that requires 12 hours The current task duration is 2 days By increasing the painter’s working day to 8 hours and keeping the painter assigned full-time to the task, the task shrinks to 1.5 days
Increase the working hours for a resource only if you want the resource to work longer hours on all assigned tasks within a given period
To increase a resource’s work schedule
1 On the Tools menu, click Change Working Time
2 In the For box, click the resource whose calendar you want to change
3 On the calendar, select the days you want to change
To change a day of the week for the entire calendar, select the day at the top of the calendar
4 Click Use default or Working time
5 To change working time hours, type the new times in the From and To boxes
Assign Overtime Work
You might at times be faced with a very constrained situation For example, you won’t be getting additional resources and all your available resources are fully occupied with task assignments each hour of their normal working day To use resources to decrease task durations, there’s only one thing left to do: assign overtime work For each hour of overtime worked, Microsoft Project calculates costs based on the overtime rate you specified for that resource (unless you indicate otherwise) Assigning overtime work can be costly, but sometimes it’s your most efficient option
To assign overtime work to a task
1 On the View Bar, click Gantt Chart
2 On the Window menu, click Split
3 Click anywhere in the bottom pane
4 On the Format menu, point to Details, and then click Resource Work
5 In the top pane, select the task for which you want to assign overtime work in the Task Name field
6 In the bottom pane, type the number of hours in the Ovt Work field for each resource
Strategies for Starting Tasks Earlier
Trang 9While cutting the project scope and reducing task durations can help you shorten your schedule considerably, you can tighten it further by making critical tasks start earlier than their original start dates When you can’t cut the scope, and reducing task durations isn’t possible or doesn’t shrink your schedule as much as you want, having tasks start earlier might be your only option
Depending on your particular situation, you can use some or all of the following methods to have tasks start earlier:
• Rearrange tasks in a more efficient order
• Break a large task into smaller tasks
• Add lead time to tasks
• Change the link type
• Change the constraint type
• Change the task type
Change the Task Sequence
The sequence in which tasks occur can affect the project duration For example, in preparation for a clockwork exhibit, the tasks "Painting the walls," "Hanging clocks," and "Arranging furniture" are scheduled for Monday, Tuesday, and Wednesday, respectively But, because the walls take 24 hours to dry, clock hanging can’t begin until Wednesday and furniture arranging is pushed to Thursday, causing the schedule to slip However, by switching furniture arranging (which doesn’t depend on the walls being dry) to Tuesday and hanging clocks to Wednesday, the project stays on schedule, without wasting days or possibly increasing the project duration It’s a good idea to check your schedule for instances where it’s more efficient to put tasks in a different order When you find those instances, you can change the task sequence by moving tasks
To move a task
1 On the View Bar, click Gantt Chart
2 Click the ID number (usually in the leftmost field of a task row) of the task you want to move
The entire row should appear highlighted
3 Click Cut Task
4 Click the ID number of the row where you want to insert the task
5 Click Paste
6 Examine the links between the moved task and its predecessor and successor tasks, changing these links as necessary
Break a Large Task into Smaller Tasks
Not all critical tasks are necessarily created equal Most of the ones in your schedule probably do correspond to a concrete, narrowly defined set of actions But some might actually correspond to several smaller but still
significant tasks, each of which should be included in your project plan as a separate task, and which you can
Trang 10then schedule more flexibly than one large task If that’s the case, you can break down these overly large tasks into smaller subtasks
Some of the subtasks may not need to be completed in sequence for the work to progress, so you may be able
to shorten the critical path by making some of the subtasks noncritical Even if some of the subtasks are critical, you might be able to overlap them or change the link type Smaller, overlapping subtasks can have a shorter total duration than the original longer task
Typically, when you use Microsoft Project to break a large task into smaller tasks, you make the large task a summary task by adding subtasks
To break a large task into a summary task and subtasks
1 On the View Bar, click More Views
2 In the Views list, click Detail Gantt or Tracking Gantt, and then click Apply
3 In the Task Name field, select a single task on the critical path that could be completed in several steps.
4 Click Unlink Tasks
5 Remove the resources assigned to this task
For information about removing resources from a task, see Chapter 8, "Assigning Resources to Tasks."
6 Select the task beneath the task you want to change, and then click New Task on the Insert menu
7 Repeat step 6 for each subtask you want to add
8 For each new task, type a name in the Task Name field and a duration in the Duration field
9 In the Task Name field, select all the new tasks, and then click Indent to make them subtasks of the original task
The original task becomes a summary task
10 Link the new tasks as appropriate
Add Lead Time to Tasks
Most likely, you’ve linked many of your tasks with a finish-to-start (FS) link, so that the successor task doesn’t start until its predecessor task finishes In some cases, that dependency might be absolutely necessary and true
to life A clock can’t be hung before it’s built But sometimes the work on a successor task can begin before its predecessor task is entirely finished The work can overlap If the museum crew prepares one gallery wall at a time, maybe they can start hanging clocks before all the walls are finished