As progress is made on your project, there are a number of things that may drive changes to your schedule model.
– Status is incorporated into the schedule.
– As more is understood about tasks, durations may need to be revised to reflect your best current estimate.
– Changes in resource requirements or availabilities may need to be incorporated.
– Additional scope may be added to the project.
The schedule model must be updated regularly to ensure that it always reflects ALL of the information known to date.
These changes will cause impacts to the plan. When you incorporate status or other changes in the schedule model, through CPM you are able to immediately see the results. You are able to see the downstream effects on your project paths and on the project end date.
In Lesson 4, in the section on Total Slack Calculations, we illustrated what happens when tasks slip. Total Slack is reduced, and the critical and near critical paths of your project may change. Analysis must take place any time status or other changes are applied to your schedule in Microsoft Project.
We need to review any variances. A variance is when the forecast information – Start, Finish, Duration, etc. – is different than the Baseline – Baseline Start, Baseline Finish, Baseline Duration, etc.
You may view the variances in your project by:
- Right clicking on the current view name and selecting Tracking Gantt.
- Right clicking at the top of the ID column and selecting the Variance table by.
- Insert the Duration Variance and Total Slack fields next to Finish Variance, and the Indicators column at the far left of the table.
The lower dark gray bar is the baseline, and the upper blue bar is the current schedule. The current schedule has % Complete filled in with a darker blue color for any tasks with progress.
Variances are calculated as Current – Baseline, e.g. Start – Baseline Start, Finish – Baseline Finish. As we previously covered, you should always make sure that Baseline reflects the current baseline as that is what is used in variance calculations.
If you see positive variance, it means you are behind schedule or over cost. If you see negative variance, it means you are ahead of schedule or under cost.
Group the tasks, by selecting the autofilter pulldown for Total Slack and selecting Group By and then Duration.
All completed tasks will have a Total Slack value of 0 days.
Your focus will be on critical and near critical paths. If a task has a variance, but has a large amount of Total Slack, you will typically not need to address it.
If your project end date has pushed out beyond the due date, or you now have tasks that do not meet your Critical Task Threshold, you will need to find a way to compress your schedule. Typically, tasks with longer Durations are easier to compress.
Schedule Compression
Schedule compression may be needed at various points during planning and execution. It could be during initial planning, after resource leveling, or as status and changes are made to the project. Any time that you have tasks that don’t meet your Critical Task Threshold, you will need to try to compress your schedule. The two common approaches to schedule compression are: crashing and fast-tracking.
- Fast-tracking – Changing schedule model logic (links) to overlap or perform in parallel, tasks that would normally be done in series.
For example, typically you want to wait until the Final Design Review is complete before ordering parts. However, if there are some long-lead parts that you need, and you need to compress your schedule, you may decide to order these parts earlier, after the Preliminary Design Review. You would modify the linking to change the schedule so that these parts are ordered after the Preliminary Design Review. Fast-tracking typically doesn’t add additional cost to the project, but it does increase risk.We are performing our tasks in a less than ideal order, to reduce the duration of our schedule. In this case, we may end up deciding on a different part at Final Review, and we still have to wait for them.
- Crashing – Analyzing, and implementing, tradeoffs between cost and schedule to determine how to get the most schedule relief for the least additional cost. We are spending money to reduce our schedule.
Crashing may include options like bringing on additional resources or using overtime so that the Durations of tasks can be reduced, or paying extra for expedited deliveries of parts.
If you are adding resources, make sure that the Duration reduction is valid. Typically, doubling the resources on a task will not cut the Duration in half, because there needs to be additional time spent in communication and coordination. However, if you are using Fixed Work task types, Microsoft Project will assume a linear change.
It is ESSENTIAL that you focus on critical (and near critical) paths when fast-tracking or crashing. These are what is driving your project completion.
If neither fast-tracking or crashing are options for your schedule, you will need to work with the Sponsor and customer to delay the due date or determine what scope can be delayed or eliminated.
You should also analyze the changes in resource requirements based on the changes in task dates. As tasks move, their resource requirements move with them. You may have had your resources leveled before starting execution, but as dates change, resource overallocations may occur. Resource information should be reviewed, and if the status or changes have caused new significant overallocations, the project may need to be releveled.
Remember that the schedule model is providing information about POTENTIAL issues. It is your role to determine ways to resolve them. It is important to be proactive in looking at potential problems and determining ways to mitigate or eliminate them. You can identify variances when they first occur and analyze the causes. The goal is to identify issues early when there are more options available to resolve them.
Your process for analyzing and responding to impacts may include modeling them into a ”What-If‘ version of your schedule. A What-If is simply a copy of your current schedule that you can use to use try out various options to determine the best way to address your potential issues.