Sometimes constraints interrupt scheduling and identifying critical path, for example, so schedulers should use as few constraints as possible. On the other hand, activity codes provide convenient functionalities for dealing with activity data, so schedulers should create, assign and use as many activity codes as possible.
ASSIGNING CONSTRAINTS
Normally, an activity’s start and finish dates are defined by its relationships with predecessor activities; however, P6 users can adjust the dates arbitrarily by assigning constraints to the activities. Constraints should be assigned to activities only as required by the client. Most clients do not allow constraints because constrains affect an activity’s total float. Thus, any constraints assigned to activities must be documented with reasons and sources. There are nine constraint types in Primavera P6: • Mandatory start – This forces early and late start dates of an activity or milestone to be equal to the constraint date, regardless of schedule logic and calculations. • Mandatory finish – This forces early and late finish dates of an activity or milestone to be equal to the constraint date, regardless of schedule logic and calculations. • Start on – This forces an activity or milestone to start on the constraint date, regardless of the calculations of the schedule, overriding schedule logic entirely. • Start on or before – This places a deadline on the start of an activity or milestone and forces the activity or milestone to start no later than the constraint date.
• Start on or after – This sets the earliest date on which an activity or milestone can begin and forces the earliest start date to be equal to the constraint date; however, if the calculated start date is after the constraint, the later date will apply.
• Finish on – This is used to force an activity or milestone to finish on the constraint date, regardless of the calculations of the schedule.
• Finish on or before – This places a deadline on the completion of an activity or milestone, forcing the activity or milestone to finish no later than the constraint date. • Finish on or after – This sets the earliest date on which an activity milestone can
finish.
• As late as possible – This consumes the free float of an activity or milestone, and pushes the activity or milestone as late as possible without impacting the start of the successors (free float).
activities – soft constraint and hard constraint. Soft constraint allows an activity to move back and forth, or in one direction, and includes Start On, Start On or After, Start On or Before, Finish On, Finish On or After, Finish On or Before, and As Late As Possible. Hard constraint is the constraint (or combination of constraints) that allows no movement, or movement only within a given range. It includes Mandatory Start, Mandatory Finish, Start On or Before + Start On or After, and Finish On or Before + Finish On or After. If, for instance, you want an activity to start between 3 January 2017 and 17 January 2017, you need to set two constraints – select “Start on or after” in the Primary constraint on 3 January 2017 and “Start on or before” in the Secondary constraint on 17 January 2017, as shown in Figure 74. Figure 74 - Constraints
ACTIVITY CODES
Activity codes are like tags, and help P6 users group and filter activities. They represent broad categories of information, such as phase, division of work (department or discipline), or location, building, floor, activity owner (responsible team, department, or staff). Activity codes can act like WBS codes, organising activities in a hierarchy and providing even more powerful features to organise them in various ways by combining several activity codes at the same time. Figure 75 shows an example of organising activities based on activity codes – Building and Floor. In grouping activities, the activity code for Building is located at a higher level than that of Floor in the image at left, and vice versa in the image at right. Thus, some P6 users prefer to use activity codes instead of WBS codes, which are less flexible and versatile than activity codes; however, there are features in WBS that activity codes cannot provide. You can summarise activities based on WBS, but not based on activity codes. Similarly, you can create a WBS summary activity in each WBS level, which shows a summary of WBS directly. Furthermore, most software packages share WBS format; thus, you can easily merge WBS outlines into other software, while activity codes can create problems.Below are the steps to create activity codes and assign them to activities: • Open the Activity codes dialogue box (Enterprise – Activity codes).
• Click Modify in the dialogue box and you will see the Activity code definitions dialogue box (See Figure 76). • Hit Add in the dialogue box, name it, and then define Max length of code value for the activity code you created. Click Close. • In the Activity codes pop-up, click Add to create as many Code values as you like, and name them. Click Close. Figure 76 – Creating activity codes Below are the steps to assign activity codes to activities:
• Display the Columns dialogue box by right-clicking on the columns of the activity window.
• Search the activity code in the Available options area and move it to the Selected options area by double-clicking it. Hit OK.
• In the activity window, select an activity, click the cell of the activity code, and you will see a pop-up asking you to select a value, as shown in Figure 77.
• Double-click the value.
• If you want to assign the value multiple activities, you can use the Fill down command.
Figure 77 – Dialogue box for selecting an activity code value