What is P6? At its heart, P6 is an application for scheduling projects. Yet as we mentioned earlier, what a project means can vary greatly. And though the end product is varied, every project shares some common characteristics:
There are deliverables (what the customer is paying for)
There is scope of work to meet the requirements of the deliverables
There is the management of:
Time
Cost
Resources (people, materials, and equipment)
Communication among the project team
Project Documentation
Risks
Purchases
A project has many phases, and these phases can be grouped in many ways using different terminologies and methodologies. One widely used and generally accepted categorization is as follows:
Initiation – deciding whether to proceed finding funding and resources
Planning – enumerating scope, creating the schedule, and planning resources
Execution – performing the work to create the project deliverables
Controlling – measuring progress and making corrective actions as the project progresses
Closing – delivering the project and reviewing lessons learned
While many people associate P6 with the Planning stage, it can be used throughout the life cycle:
Initiation: An initial project can be created to estimate the schedule, cash flow, and resource usage for projects that are still in the initial "what if" stages. Chapter 14, Capacity Planning and ROI and Chapter 16, Resource Management can help you decide on what projects make best sense to pursue and how pursuing those projects will affect your overall portfolio.
Planning: Obviously, P6 can be used to create the project plan. This ability should never be underestimated, as the intelligent implementation of the CPM scheduling algorithms is the heart of what makes P6 the highly-valued tool that it is today.
Execution: As the project progresses, the schedule is updated and adjusted as actual work is performed. Updated statuses can be entered directly into P6 and/or can be driven by timesheets.
Controlling: As the situation on the ground changes and activities are completed, the scheduling algorithms will update the schedule to reflect new realities. P6 will show changes in anticipated resource usage and cash flow, so that you can alter the planned work as needed to stay on target.
Closing: As the scope is completed, resources can be released to other projects. The completed project can then be converted to a project template (Chapter 10, Project Template), using the actual durations and resources expended to complete the project. Basing new projects on completed ones gives a well-grounded basis for estimating new projects.
At its core, P6 helps you manage these entities by breaking a project down into two main components: Activities and Resources.
An activity is a logical element of work to be done. Activities can occur independently, or can depend on one another. Managing the dependencies of activities is a core strength of P6.
When I was first learning software development, there was a certification test from Microsoft called Analyzing Requirements and Designing Solution Architecture, or the ARDSA. A common question on the test was to put a set of tasks into the best order to complete the work. For example, the job would be to turn on a flashlight. You are given a battery tester, a dozen batteries, only six of which work, and a flashlight that is broken down into three components: the case, the front casing, and a light bulb. What is the best way to order the following tasks?
Turn on flashlight
Test batteries
Screw front casing onto case
Insert batteries
Identify two working batteries
Insert light bulb into front casing
Solving such a problem may seem trivial at first. We make such decisions every day in our personal lives. But when the end product is not simply assembling a flashlight, but designing, building, and commissioning a power plant, the steps involved become quite complex. There are tasks within tasks, multiple teams to coordinate, and equipment to be delivered and assembled. A simple checklist will no longer suffice, and a single person cannot keep it all in his or her head. Activities track the disparate tasks required, and the relationships between activities form a network of dependencies that can be managed and modified with P6.
An activity can also have resources. Resources can be the people assigned to work on the task, the equipment that is needed to perform the work, or the materials to install. Each of these resources has an associated cost, and potentially limited availability. Knowing what resources you will need when and where is crucial in being able to make long-term plans on complex projects. For example, if you are sending a team to the South Pole station to assemble a new telescope, the logistics can be daunting, with a limited number of trips available in a given season. Heaven forbid that you send that team down and neglect to provide them with an essential piece of equipment. They can hardly drive down to the nearest Home Depot!
Resources also have calendars – when a given resource is available. For people, this is their work schedule. For equipment, there may be limitations on when it can be used based on weather, or a maintenance schedule. For the previous example, there is a calendar of when supplies and people can arrive at the station. If your team is working in arctic regions, there are seasons when the ground is too muddy to move equipment, and getting to the site can only be done during months when the ground is frozen.
There are also more mundane calendars. You may want to minimize the amount of overtime paid on a job, which can cut into profits. Certain employees may have religious holidays that affect the work schedule.
P6 posits resources as first-class citizens of the scheduling world. And it gives you the ability to manage resources across all of your projects, giving you the ability to make decisions from a high level.