In a large and complex schedule, large numbers of changes and assignments to activities take long time. Oracle Primavera P6 Global Change tool enables to modify some significant features and components of the activities. Activity types, resource assignments, calendars, budgeted units or other elements can be changed easily and quickly.
Utilising the Melair Risk Management Tool, “ATOM”, requires each selected risk activity to have a “Calculated Duration” which is calculated from the three time estimates of:
- Pessimistic Duration
- Most Likely Duration
- Optimistic Duration
In other words the original PERT calculation of (a + 4b+ 6) /6. Oracle Primavera P6 does not provide the PERT facility, thus it is necessary to use the P6 Global Change Tool, which is a time saving tool that enables the user to make global adjustments in a short time span without changing the activities one by one. This paper shows how to calculate the activity “Estimated Duration” by using the Oracle Primavera P6 Global Change tool having defined the three time durations using the UDF function.
Defining three time estimates to calculate PERT Expected Duration using UDF’s
In project management, Project Evaluation Review Technique or PERT is used to identify the time it takes to finish a particular task or activity to take into account estimating doubt It is a system that helps in proper scheduling and coordination of all tasks throughout the project.
It also helps in keeping track of the progress, or lack thereof, of the project. In the 1950s, Project Evaluation Review Technique was developed by the US Navy to manage the Polaris submarine missile program of their Special Projects Office.
Oracle Primavera P6 does not support the PERT technique directly, but through the use of the UDF function and Global Change function the PERT technique can be emulated to produce the “Expected Duration”
The three UDF’s are
- MOST Time representing the Most Likely Duration
- OPTD Time representing the Optimistic Duration
- PESS Time representing the Pessimistic Duration
The “Expected Duration” is also defined as a UDF, these are shown below
Note that the Data Type must be defined as “Integer”
The ATOM activities are filtered and the three point estimate durations are entered to the PESS Time, OPTD Time and OPTD Time as shown below
Oracle Primavera P6 Global Change
To use Oracle Primavera P6 Global Change tool, select Tools >Global Change from the main drop down menu at the top of the screen. This will display the Pre-set Global Change window in the below figure, Figure 1.
Figure 1 – Primavera P6 Global Change Tool
Click “New” button and select “Activities” for the Select Subject Area. Type the Global Change Name as “PERT Calculation”, Figure 2.
Figure 2 – Name “PERT calculation”
Click in the IF statement “Parameter” cell and select (All of the Following) from the drop down box, Figure 3
Figure 3 –From parameter drop down select “Where”
Figure 4 – Where
In the parameter cell scroll down to the UDF “MOST Time”
Figure 5 – Select “MOST Time” from the drop-down menu
In the line “Where” click in the cell under “Is” and from the drop-down menu select “is not equal to” and in the value cell enter the value “0”. The reason for this is to select only those ATOM tasks which have a value greater than zero as is shown in Figure 6 below.
Figure 6
Next click in the “Then” section and click Add to highlight the next selection for the parameters to calculate the estimated duration. Select from the Parameter drop down menu “Expected Duration” as shown in Figure 7, note that the is cell has = as a default entry
Figure 7 – Select “Expected Duration
Figure 8 – Select MOST Time
The PERT formula as shown above indicates that the Most Likely duration is multiplied by “4”, In the Operator cell choose * from the drop down menu. Click In Parameter/Value and select {Custom}, click on it, then enter the value “4”
Figure 9 – Select “{Custom}
Figure 10 – Value entered “4”
Having multiplied the Expected Duration “MOST Time” by 4, P6 will calculate that value, next select “Add” and in the Parameter cell select Expected Duration once again from the drop-down list. Next in the Parameter / Value cell, select Expected Duration again (this will contain the value as calculated from the line above) set the operation to “+”.
Next select “PESS Time” from the drop-down menu in Parameter / Value. Once again select Add and then select Expected Duration from the drop down menu in the Parameter / Value. Repeat the process again for the OPTD Time. Select “Add” once again, selecting Expected Duration in both Parameter Cells, but this time select “/” as the Operator and s we require the accumulated value in “Expected Duration” to be divided by 6.
Remember that when selecting the final parameter P6 will show “{Custom} as the first line, click and then enter 6 in the cell. The result will be that value of expected Duration will the result of “PESS Time” + MOST Time * 4 + “OPTD Time” divided by 6. Figure 11 shows the completed Global Change.
Figure 11 – Global Change Parameters
Now click the OK and the list of Global Change’s will appear, select the Name “PERT Calculation to execute the change, by selecting “Apply Change”
This will produce the following message
To execute the Global Change, select Yes, and the following report list is generated
If the calculations are correct, click the Commit Changes button on the bottom.
Entering “Yes” produces the following dialog, enter a file name, e.g. Global Change ATOM 12-04-19
In the Global Change listing, the changes that have been implemented are shown. For each activity the log shows the results of each activity before and after the execution of the Global Change. In the example above, each task, the cumulative values are shown, there are four lines, as there were four parameters in the Global Change parameter definition.
The final value in the right-hand column is the Expected Duration as calculated by the PERT technique which means activity A1507 has an Expected Duration of 18, for A1517 has an Expected Duration of 25. For A20245 it is 63 and for TO70-022 is 42
Summary
Oracle Primavera P6 Global Change tool is very useful to make changes in large and complex projects. Many necessary calculations can be done by the help of the parameters defined in the “Modify Global Change” window. The subject areas for the assignments can be activities, activity resource assignments, and project expenses.