prim35271:How does Project Management perform Levelling?

Answer 1:  Resource Levelling is a process which helps to ensure that sufficient resources are available to perform the activities in your project, according to the plan.  Resource Levelling works by moving an activity to a time when it’s resources are all available to work on the activity and as such can push out the end date of your project.  Resource Levelling can be performed against any resource, regardless of the Resource Type (Labour, Non Labour and Material resources can all be leveled).

To perform Resource Levelling on a project, go to Tools, Level Resources.

Answer 2:  Scheduling the project (without Levelling it) will remove any changes to dates that were made by Levelling the project.

Question 3:  How does the Leveler decide the order in which activities will be leveled?

Answer 3:  Activities enter the Leveler one at a time.  The order in which activities enter the Leveler is decided as follows:

1. All activities without predecessors (or whose predecessors have all been leveled already) are considered first
   Note:  Logic is always obeyed when Levelling: an activity cannot enter the leveler until all of it’s predecessors have been leveled.
   


2. If there is more than one activity without a predecessor, or with leveled predecessors, Levelling priorities are used as a tie breaker
   Note: Levelling priorities can be viewed and set at Tools, Level Resources in the “Levelling Priorities” section
   


3. If there is still a tie, after Levelling priorities have been considered, Activity ID is used as the final tie breaker
   Note:  Activities from different projects may have the same Activity ID which would seemingly produce another tie.  However, the Activity ID which is used to break the tie is the data’s “internal” Activity ID, which runs in order of the time and date of the activity’s creation.
    

Answer 4:  Once an activity enters the leveler, it’s resource assignment’s Remaining Units/Time is compared with the relevant resource’s Maximum Units/Time (less any hours already used by other leveled activities on that date) for each day the activity is due to work.

• If the Resource’s Maximum Units/Time is greater than the resource assignment’s Remaining Units/Time then the resource is available to work and the activity is scheduled to start
   


• If the Resource’s Maximum Units/Time is smaller than the resource assignment’s Remaining Units/Time then the resource does not have enough time to allocate to the activity and the activity is moved until the Resource’s Maximum Units/Time exceeds the Activity’s resource assignment’s Remaining Units/Time for every day of the Resource Assignment’s duration.

Example:  A program has three activities, which enter the leveler in the order A, B, C.  All three activities have the same resource assigned whose Maximum Units/Time is 8h/d.  None of the activities have any predecessors and without Levelling all three would therefore start on the data date (day 1)

Activity A needs its resource for 6h/d across 3 days.
Activity B needs its resource for 4h/d across 2 days.
Activity C needs its resource for 2h/d across 6 days.

Step 1.  Activity A enters the leveler:

Activity A’s Remaining Units/Time (6h/d) is less than the Resource’s Maximum Units/Time on days 1, 2 and 3.
Therefore Activity A can start on day 1 and finish on day 3.

Step 2.  Activity B enters the leveler:

Activity A has already been leveled so the Resource only has 2h/d remaining on days 1, 2 and 3.
Activity B’s Remaining Units/Time (4h/d) is more than what’s left of the the Resource’s Maximum Units/Time on days 1, 2 and 3.
Activity B’s Remaining Units/Time (4h/d) is less than the Resource’s Maximum Units/Time on day 4 and day 5
Therefore Activity B can start on day 4 and finish on day 5.

Step 3.  Activity C enters the leveler:

Activities A and B have already been leveled so the Resource only has 2h/d remaining on days 1, 2 and 3 and 4h/d remaining on days 4 and 5.
Activity C’s Remaining Units/Time (2/d) is less than what’s left of the the Resource’s Maximum Units/Time on days 1, 2 and 3.
Activity C’s Remaining Units/Time (2/d) is less than what’s left of the the Resource’s Maximum Units/Time on days 4 and 5.
Therefore Activity C can start on day 1 and finish on day 6.

Question 5:  How do constraints affect Levelling?

Answer 5:   All constraints are honoured during Levelling except As Late As Possible and Expected Finish constraints which are ignored during Levelling (i.e. Activities with only As Late As Possible and/or Expected Finish constraints will be leveled in order of their relationships and Levelling priorities, regardless of their constraint)

• Activities with mandatory constraints are leveled first regardless of relationships and Levelling priorities. 


• Activities with non-mandatory constraints are leveled in order of their relationships and Levelling priorities.

Answer 6:  Resource assignments in closed, summarized projects which have an equal or higher Levelling priority (where 1 is the highest possible Levelling priority, 100 the lowest) to the project being leveled will be considered ahead of the resource assignments in the project being leveled.  If two or more projects are open, their activities will be considered equally, as though they were all part of the same project.

Example 1:  Project A has a Levelling priority of 20, Project B has a Levelling priority of 10, both projects are open, “Consider assignments in other projects with a priority equal/higher than…” is switched on and set to 15.  Because both projects are open, the “Consider assignments in other projects with a priority equal/higher than…” setting is ignored and both projects activities are considered for Levelling as though they were in the same project.

 
Example 2:  Project A is open and has a Levelling priority of 20, Project B is closed and has a Levelling priority of 10, “Consider assignments in other projects with a priority equal/higher than…” is switched on and set to 15.  Because Project B is closed and has a Levelling priority higher than 15, Project B’s resource assignments will be considered before Project A’s activities are levelled.

Fig 1: Projects A and B, scheduled, but not levelled:

Fig 2: Both projects are summarized, Project A is opened and then levelled:

Answer 7:  This option allows the scheduled early and late dates to be retained in the Early Start and Early Finish fields and shows the Levelled dates in the Remaining Early Start and Remaining Early Finish fields.  The Remaining late dates are the Scheduled rather than the Levelled late dates.  The Levelled float is stored in the Remaining Float field.

If this option is switched off then a backwards-pass of Levelling is also performed, meaning that the late dates may be moved earlier if over-allocation has occurred or if a successor has been delayed.

The differences between the Levelling Forward and Backward passes are detailed below:

Question 8:  How does the option “Level resources only within activity Total Float” affect Levelling?

Answer 8:  This is a useful option to use if your time deadline is more important than your resource deadline because it allows you to choose to over-allocate resources.  This option will not create negative float when Levelling and can only be used if Preserve Early and Late Dates is switched on.  If Level Resources Only Within Activity Total Float is used, the process of deciding when an activity can happen is as follows:

1. The software will try to place the activity on its early dates.  If there is enough resource availability, the activity will stay on its early dates.  If there is not enough resource availability, the software moves to Step 2
    


2. The activity is moved forward one work period and the resource availability is checked on these new dates.  If there is not enough resource availability, the software returns to Step 2.  If there is enough resource availability then the activity is Levelled on these new dates.  If there is not enough resource availability and the activity’s Total Float is less than the Preserve Minimum Float When Levelling setting the software moves to Step 3
    


3. The Resource’s Maximum Units/Time setting is (temporarily) increased by the percentage in the Max Percent to Over-Allocate Resources setting.  The software then returns to step 1, this time using the raised limits
    


4. If the activity cannot be placed within the float and the raised Maximum Units/Time limits, the activity will be placed on its early dates and the Scheduling / Levelling Log will show that the activity could not be Levelled

Answer 9:  The activity will be placed on its early dates and the Scheduling / Levelling log will show that the activity could not be Levelled

Question 10:  How does activity type affect resource assignment Levelling?

Answer 10:  The following rules apply to Levelling resources:

• If you level a Task Dependent type activity with driving and non-driving resource assignments, the Project Management module requires that all resources be available in order to place the activity.
   


• If you level a Resource Dependent type activity with driving and non-driving resource assignments, the Project Management module requires that all driving resources assigned to the activity be available in order to place the activity. All non-driving resources will be Levelled on or after the activity dates, which are driven by the driving resources.
   


• If you level a Resource Dependent type activity with non-driving resource assignments, the Project Management module will place the resources on or after the earliest possible start date of the activity. These resources can be placed any time in the future after this candidate date.
   


• If you level a Resource Dependent type activity with a combination of driving and non-driving resources, and the driving resource succeeds in finding availability, while the non-driving resource fails, the non-driving assignment dates will be delayed based on where the driving resources are placed.
   


• WBS Summary and Level of Effort activities are ignored during the Levelling process.

Answer 11:  Yes, the flow-chart can be downloaded here:  Resource Levelling Flow Chart.pdf (8kb)