What do predecessors mean in Microsoft Project

Fixed units - transaction types in MS Project (1)

+++ Species diversity - The types of operations in MS Project +++ Part 1: Fixed units +++ What you should know and how to work with it correctly +++

By Martin Göhe, PMP

If you have planned tasks with manpower resources or updated tasks in Microsoft Project, you may have wondered at one time or another about the seemingly “idiosyncratic” behavior of the tasks.

In the current three-part blog series "Species Diversity - The Types of Operations in MS Project" I would like to show you the types of operations

present in detail and show you that Microsoft Project is only consistent in its behavior, which is sometimes difficult to understand.

Tip for beginners: You can find an overview of the transaction types in my blog post Planning options in MS Project under the heading "Standard transaction type".

Standard task type in Microsoft Project

With MS Project, the default transaction type is Fixed units. The standard transaction type is stored in the Option settings set. By clicking on the tab file takes you to the MS Project Information page.

Fig.1: Ribbon file

Select the entry there Options out.

Fig.2: Call up option settings

The project options are displayed. Under Scheduling in the section Planning optionsn for this project you will find the set standard transaction type. At this point you can define one of the 3 transaction types in MS Project as the standard transaction type. If you make a change at this point, remember to confirm the change with OK.

Fig.3: Set standard transaction type

Whenever you create a new activity in your project plan, the default activity type you have selected is assigned to it. So in our case Fixed units. For existing processes, you can change the process type at any time directly on the relevant process. I will describe how to do this later in this article.

Work resources in Microsoft Project

The transaction types come into play in project planning when planning is carried out with work resources. For the subsequent analysis of the behavior of processes with Fixed units I will work with two resources: Anna and Bernd.

  • Anna is a full-time employee. She works 8 hours a day Monday through Friday. Your maximum units are therefore 100% based on the standard calendar from MS Project, which defines a working day with 8 hours per day.
  • Bernd, on the other hand, is a part-time worker. Its maximum units are therefore 50% on the standard MS Project calendar.

Fig. 4: Resource data

Calculation logic

MS Project always uses the following formula:

Duration = work / units (in% * hours per day according to the resource's base calendar)

If the duration of a task is specified and a resource is then assigned with its unit value, MS Project calculates the work.

For a task with a duration of 5 days to which a resource is assigned to 100%, this results in a work volume of 40 hours.

So it's a simple 3-variable equation. This means that 2 variable values ​​must be given so that the third variable can be calculated.

Task dimensions in Microsoft Project

When planning with work resources, it is important to distinguish between two task dimensions:

  • Temporal dimension (Duration)
  • Effort-related dimension (Job)

The time dimension (duration) describes how much time is available for a process and of course when it begins and ends.

The effort-related dimension (work) describes how much work should be done for a task.

So it's about the question of how much work should be done and in what duration. The ratio of duration to work is not necessarily 1: 1. 5 employees who are 100% assigned to a task with a duration of 5 days can work 200 hours.

Create a suitable view

When I work with resources, I like to use a split view. In the upper area I display the Gantt chart and also hide the columns Art and job (right-click in the table header and then select the desired column).

In the lower area I use the view Process: mask work. To do this, go to the ribbon view, activate Details and choose there Process: Mask off. Then click with the right mouse button in the gray area of ​​the lower part of the view. A selection dialog appears. Select the entry job out.

Fig.5: Split view with Gantt chart and process: Work screen

Change transaction type for transactions

As mentioned earlier, you can change the task type of a task at any time in your project plan. There are two ways of doing this:

  • Click in the column Art and select the type of transaction you want from the menu.
  • Alternatively, you can also use Process: mask change the transaction type.

To do this, mark the process that you want to edit in the upper part of the view. In Process: mask the data of the selected process are displayed. Now select in the field Transaction type the transaction type. The button OK is displayed. Confirm the change made with OK.

initial situation

For the investigation of the behavior of processes of Art Fixed units let us assume the following initial situation:

  • Task 1 and Task 2 each have a default value of 5 days.
  • Task 3 andTask 4 have a duration of 5 days and a work volume of 40 hours as default values.
  • Task 5 and Task 6 have a default value of 1 day each (newly created tasks always have a duration of 1 day in MS Project) and a work volume of 40 hours.

Fig.6: Initial situation before the resource allocation

Resource Allocation

There are two ways to assign a resource:

Possibility Number 1: You can assign a resource by clicking in the row of a task in the column Resource name click and select the required resource from the selection menu. In this case, the unit value stored in the resource table for the resources (100% for Anna and 50% for Bernd) is used in the calculation.

Option 2: You transfer the resource Process: mask work to. To do this, mark the desired process in the upper area of ​​the split view. In the lower part of the split views, the data of the previously selected process are displayed. Then click in the column Resource name and select the required resource. Confirm your selection with OK. The units from the resource table are also used here, unless you specify otherwise.

Personally, I prefer the second option of resource allocation, since the calculation results are included here after confirmation OK and I can adjust all values ​​directly at any time if corrections are necessary.

Tip: Do you want to assign a resource to an activity with a different unit value (than the one stored in the resource table)? That's overProcess: mask work possible. Choose in Process: mask work the resource, write in the column units enter a different value and then confirm with OK. MS Project now uses the unit value you entered for the calculation.

After all the resources are allocated, we get the results shown in Figure 7. The red "men" in the indicator column mean that the resources are overloaded. This aspect is ignored here because we want to concentrate on the behavior of the transaction types.

Fig. 7: Results of the resource allocation

For Task 1 and Task 2 the duration of 5 days was specified. Anna was given 100% (i.e. with an availability of 100% * 8 hours per day) on the Task 1 assigned. According to the calculation logic of MS Project, a work volume of 40 hours is calculated for the process. At Task 2 a work volume of 20 hours is calculated because Bernd was assigned 50% (i.e. with an availability of 50% * 8 hours per day = 4 hours per day).

In short: the respective duration of the processes was specified (variable 1) and when resources were allocated to the processes, the resources brought their respective maximum units (variable 2) with them. Of the 3 variables of the calculation logic (duration, work and units), 2 variables (duration and units) are given and thus the third variable, work, can be calculated.

Looking at the results of the resource allocations on Task 3 and Task 4 shows how the selected transaction type influences the calculation. The duration (5 days) and work volume (40 hours) were specified for both processes.

For Anna, who is available 8 hours a day, the work volume of 40 hours can be completed in 5 days.

For Bernd, on the other hand, who is only 50% available - i.e. 4 hours per day - the specified work volume of 40 hours cannot be completed in the specified duration of 5 days. MS Project therefore recalculates the duration: 10 days instead of the original 5.

How can this be explained?

The transaction type Fixed units MS Project “forbids” to recalculate the units of the assigned resource. This means that of the three variables of the calculation logic, the unit value (variable 1) of the resource is fixed.

On the other hand, under this prerequisite, the work volume of 40 hours (variable 2) can no longer be completed in the specified duration (variable 3) of 5 days. MS Project must resolve this conflict and calculated therefore the duration New.

The same applies to the processes Task 5 and Task 6. The duration of 1 day each and the work volume of 40 hours each are specified. Since the transaction type forbids the adjustment of the unit values ​​and the work volume of 40 hours cannot be performed in the specified duration of 1 day, MS Project adjusts the duration again: 5 days for Anna and 10 days for Bernd.

Changing the variables for resources that have already been assigned

In the Resource Allocation section, I showed you how type Fixed units behave when they are first assigned a resource. Now I would like to show you what happens if you open the variables with the resource already assignedDuration, job and units to change.

Changes to the duration of the transaction type Fixed units

If a resource is assigned to a task, the equation of the calculation logic is balanced. All 3 variables (duration, work and units have a value).

If you now change the duration of the process, MS Project must recalculate the equation so that it is balanced again. MS Project recalculates the work.

The explanation is obvious: The units of the assigned resources must not be changed by MS Project, since the transaction type Fixed units is. The first variable is therefore fixed. The duration is the second variable, the value of which is changed so that only the work as the third variable can be recalculated.

This can be seen very clearly if, for example, you look at the Duration of task 2 increased from 5 days to 6. MS Project now calculates the work volume for the task at 24 hours, because Bernd is 50% available (6 days * 50% * 8 hours / day = 24 hours).

Fig. 8: The work is recalculated for an assigned resource if the duration is changed.

Change of work in the transaction type Fixed units

If the work of an activity is changed to which a resource is already assigned, the duration is recalculated. The units are fixed, the work is changed so the equation can only balance out by having Microsoft Project recalculating the duration.

When the work of Task 1 is increased from 40 hours to 60, the result is a new duration of 7.5 days.

Fig. 9: The duration is recalculated for an assigned resource if the work is changed.

Change of the units for the transaction type Fixed units

Let us now consider the situation when the resource has already been assigned and we subsequently change its unit value.

On Task 6 is assigned to Bernd with 50%. For example, if you increase this value to 100%, Microsoft Project will use Fixed units again recalculate the duration to balance the equation. Now the duration is only 5 days instead of 10.

Fig. 10: The duration is recalculated for an assigned resource if its unit value is changed.

You might be interested in that: Conditional formatting of activity bars - MS Project tip

When should you use the transaction typeFixed units apply?

Now that we've seen how a process works with Fixed units behaves in detail during project planning, we can answer the question when it makes sense to plan with this type of transaction.

Tip: The transaction type Fixed units are ideal planning options if you need to ensure that the proportion of working time per day (units) with which you assign a resource to a task should remain constant when the duration (time dimension) or the work (resource-related dimension) changes .

Activity update and project update in Microsoft Project

In the next step I want to show you how a process works with Fixed units is planned to behave when collecting progress data.

Important: We are no longer in the planning phase of the project, but in the implementation!

The project staff carry out the planned work and your task as the project manager is to record the progress data sent to you and to update the project plan.

initial situation

  • Our project consists of the processes Task 1a, 2a, and 3a each with a successor Task 1b, 2b, and 3b
  • All processes have one Duration of 5 days
  • a 40 hours of work and
  • each is one Full time resource (Bernd is now also 100% available).

Fig. 11: Initial situation for the process update

In addition, I have the columns

  • % Completed,
  • Actual duration,
  • Remaining time,
  • Job,
  • % Work completed,
  • Actual work and
  • Remaining work

inserted into the table.

Set and display the status date

First the status date is set. The status date is the date to which we refer when updating. The status date is shown in the ribbon Project in The Field Status date detected.

To display the status date in the Gantt chart, right-click in the graphic. A selection dialog appears. There you select the entry Gridlines out. In the grid line dialog that is then displayed, select Status date and put the Line style and the Line color firmly. Confirm your changes with OK.

Fig. 12: Set the status date and display it as a red line.

The status date forms, if you will, the Border between the past and the future. When a project is updated, you first look into the past of the project from the status date. All activities with a start date to the left of the status date must have started according to the plan. If the end date of an activity is to the left of the status date, this should be completed according to the planning.

For all processes to which the above-mentioned characteristics apply, you as the project manager must inquire about the progress data and transfer it to the project plan.

Relationship between task and resource status

When progress data is recorded with MS Project, it is mostly % Completed used. % Completed indicates how much of the planned duration of a task has been used.

  • 100% means that total duration of the operation has been used up and the process is complete.
  • 50% means just that Half the duration of the task was consumed.

It is assumed that the consumption of time is also a measure of progress.

If you are with % Completed and work with resources, please note that between % Completed and % Work completed there is an interaction. The option When the task status is updated, the resource status is also updated is activated by default in MS Project.

Fig. 13: Option When the task status is updated, the resource status is also updated

So if you set the value 50 for % Completed this value is automatically entered in the field % Jobcompleted taken over and vice versa. MS Project therefore assumes that when 50% of the time is used, 50% of the work has been done.

Record progress data in Microsoft Project

For the operations Task 1a, 2a and 3a you asked your team about the progress data.

  • Task 1a was processed as planned. So you contribute the value 100 % Completed a. The actual duration corresponds to the planned 5 days, the remaining duration is 0 days and the checkmark for completed is displayed in the information column. The same applies to the fields that relate to the work, since the task status updates the resource status.
  • Task 2a was processed faster than planned. Only 80% of the planned duration was required and no further work is necessary. In this case you contribute the value 80
    % Completed and the value 0 in the field Remaining time a. The moment you set the remaining duration to 0, the value in % Completed adjusted to 100%. At the same time, the duration of the process is reduced to 4 days, since only 4 days were actually required. By reducing the duration, the work volume is reduced from 40 hours to 32 hours (see above, behavior when changing the duration of the task) and the remaining work is also set to 0. The beginning of the successor task 2b moves forward.
  • Task 3a was started as planned, but only 40% of it was completed. In this case, you contribute the value 40 % Completed a. The dark blue progress bar is smaller than the progress bar.

Fig. 14: Progress data acquisition

Project update in Microsoft Project

However, it is not done with the recording of the progress data. The task now is to update the project plan as a whole based on the recorded progress data. Which is also urgently needed, since we have Task 3a in our project plan, which was not processed as planned.

The result is that we have leftover work in the past. This remaining work can only be done in the future. That means we have the Push remaining work from the past into the future must, i.e. in a period to the right of the status date.

Microsoft Project offers the function Update project. It is located in the ribbon Project.

If you click the ProjectTo update click, the corresponding dialog opens. There you select the option Postpone the start of incomplete work to Date and For: Entire project and confirm this with OK.

Fig: 15: Update project

After the update, the following situation arises, which is shown in the following figure:

Fig 16: Project after the update

For Task 1a and his successor Task 1b nothing has changed. Task 1a was carried out according to plan and therefore there are no effects on its successor, Task 1b.

At Task 2a and 2 B however, one sees a change. Task 2b now starts again on 03/25/18 and it became an activity restriction "Start not earlier than" set, which is represented by the calendar symbol in the information column.

How did that happen?

  • After the progress data from Task 2a were recorded, the duration of Task 2a von 5 days on 4.
  • The successor Task 2b can thus start arithmetically earlier, namely on 03/23/18. Moving the start date of Task 2b also pushed the associated work forward. This leaves us with remaining work in the past (to the left of the status date). With Update Project, this remaining work from the past is carried over into the future (to the right of the status date). To ensure that work does not slip back into the past, MS Project does not set the start date restriction earlier than.
  • The result of Task 3a and 3b you probably won't be too surprised now. You certainly expected the result. Task 3a is late and the remaining work from the past is carried over to the future. As a result, the successor 3b will start later.

Nonetheless, this constellation has a MS Project peculiarity that may make one or the other user doubt his arithmetic skills.

Take a look at the duration of process 3a. Do you notice something? The process starts on Monday, 03/19/17 and ends on Wednesday, 03/28/17. That is 8 days (excluding the weekend). However, the duration is given as 5 days.

How can this be explained?

For operations with Fixed units interruptions shown as a dotted line are not counted when calculating the duration. MS Project sees the work volume of 40 hours and calculates that this will be processed in 5 working days, which the calendar defines as 8 hours. The duration is therefore 5 working days and not 8 calendar working days.

If we look at the type of transaction in the third part of this series Fixed duration investigate, this issue will become very important. In case of Fixed duration MS Project would in fact state the duration of the process as 8 days.


What to do with what to do in this blog post Fixed units have learned:

  • MS Project uses the formula when calculating activities with work resources:
    Duration = work / (units in% * hours per day according to the resource's base calendar)
  • The transaction type Fixed units MS Project “forbids” to adjust the unit value with which a resource was assigned to a task.
  • If the task duration is given and a resource is assigned to the task, the work is calculated.
  • If the duration and work are specified, MS Project calculates the unit value for the assigned resource.
  • If you change the work or the unit value for a task to which a resource has already been assigned, MS Project recalculates the duration.
  • If you change the duration of an activity to which a resource has already been assigned, MS Project will recalculate the work.
  • Process interruptions, which can occur, for example, during the project update, are not taken into account in the process duration.

You can also find a brief introduction to the transaction types in this video:

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