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Topics: Resource Management, Scheduling
Are we missing something about the Resource Calendars?
As far as resources are concerned, there can be 2 approaches to its management:
1. When is resource the Required?
2. When is resource the Available?

In PMBOK (, we can find mention of resource calendar to be:
A resource calendar identifies the working days when each specific resource is available.

But where do we have the calendar which suggests, when are they required? Are we deeming that we can not estimate when we may require the resources?

The moment, we define the project schedule, can't we also create a schedule of the resources requirements?
Rather than designing the project schedule as per the resource availability, why not do it otherwise? Resources do not form the Baseline in the project, the Schedule does. So, I strongly feel Project Schedule should dictate the Resources provision. (please refer "Estimate Activity Resource" and "Develop Schedule")
So, once the project schedule is created, we should develop a calendar as per which the resources should be made available.

Could not find any such document or concept under Resource Planning Process Group in PMBOK. Am I missing something here, or there is no such document?
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Project Schedule development is an iterative process and recuring activity during the project. The first loop may not consider resource constraints but just apply estimates for activity durations to the network diagram. Then you will see the bare resource requirements. Now resource leveling and applying resource calendars set in, because you need to make the schedule realistic in terms of resource allocation.
So you loop until you get schedule that not only satisfies dependencies between activities but also is feasible and has a good usage of resources.

It may help you to browse the Practice Standards for Scheduling and for Estimating to get a better understanding.

A project manager always has to balance constraints and live with a compromise.
What you are asking is a common mistake in the practice (I am not saying you are doing that) because some project managers forget to update the project calendar and the resource calendar when started planning. Those are a critical input when you estimate activity duration. That´s the place where you are considering both calendars. Resource calendar is something that has to be created and maintained at organizational level.
Hi Thomas. I second your opinion and deeply appreciate the fact that the picture gets developed progressively and ideally speaking there can not be a rigid sequence to it.
However, as a matter of theoretical representation, I do feel that may be adding "Create resource requirement map" would give us a chance to sit and contemplate on the timing of the resources availability. Hence thought what if it was there in the Process Group and Knowledge Area Map.
Thanks for the reply....
Thanks Sergio for your inputs!
1 reply by Sergio Luis Conte
Aug 16, 2020 8:16 AM
Sergio Luis Conte
You are welcome.

the 'resource requirements map' may be seen as a part of the scheduling model, e.g. a resource histogram. Several tools support resource based scheduling, allowing to distribute effort over duration in several ways (front- or end-loaded, equal distribution), and hence optimizing resource usage.
Aug 16, 2020 8:03 AM
Replying to akash hedau
Thanks Sergio for your inputs!
You are welcome.
Critical Path Method calculates project schedule ignoring resource constraints. As the result you will get project resource requirements if resources are not limited.
Entering resource availability constraints and leveling your schedule you will get resource requirements that do not exceed their availability.
Resource calendar describes time periods when this specific resource can work, nothing else.
After going through all the above discussions, I feel
1. Resource Calendars are important. Because, since the projects are agile and progressively explored, it is valuable to have information regarding the availability of the resources. This enables PMs to simply pick the available resources and get the job done.
2. What I was suggesting (resource requirement calendar), is not present explicitly in PMBOK process map. However, it is implicitly developed while realizing the project schedule through schedule and resource levelling.
So, this is what is the sequence I infer now:

Identify activities
Estimate activity duration(Ignoring resource calendar)
Create network diagram (tentative schedule estimate by simply adding the time of all these activites)
Apply resource and schedule levelling to create final schedule.

Also, we may never need to create resource requirement calendar because in Agile, the progressive backlog refinement and frequent changes will add huge redundancy in creating such a calendar.

Have I inferred correct? Thanks.
1 reply by Sergio Luis Conte
Aug 18, 2020 3:04 PM
Sergio Luis Conte
The common process to follow is:
Step 1: Estimate the size of the product
Step 2: Estimate the effort (man-months)
Step 3: Estimate the schedule or duration (calendar months)
Duration is qty of product / resource capacity.
That´s because it is important to have the calendar resource and the rbs (resource breakdown structure) on hand.
A couple of resources for you:
- PMI's Standard for Portfolio Management
- the following article on PMI's website:
...- Portfolio resource management - the most significant challenge to project management effectiveness

I think you're on the right track, when dealing with shared resources. Individual projects can identify when they will require specific resources, but managing overall resource availability happens outside of the individual project. This is, in part, because when there is an availability conflict between projects regarding when a resource is "required", somebody is either going to have to wait or get a different resource. The individual project manager will need to make the case for getting the resource, but won't be making that decision.
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