and Why It Is Important 02 Defining Multiple Critical Activities in Primavera P6 03 Assessing Critical Activities Reliability 04 Managing Critical - Near Critical Activities 05
2 options to define critical activities: If a project has several deadlines (constraints), this option is useful to track the total float of each deadline Longest path is useful to focus on sequences that determine overall project completion, the amount of delay in the longest path shall be equal to the amount of delay to project completion Longest path Total float ≤ 0
in Primavera P6 By default, P6 will define critical activities as total float less than or equal to zero Both options will result the same float number All sample schedules in this material use “Total Float less than or equal to 0” as critical activities definition, simultaneously longest path is seen through activity column Alternative way to see longest path is by showing “Longest Path” column in activity window
Critical is not always Longest Path Show these columns in P6 to see critical and longest path Sample Schedule Critical Sequence Critical Longest 1 M01 > DA1 > DB0 > PB0> M03 Yes Yes This sequence is determining Project Finish date at current state 2 M02 > PC0 > M03 Yes No This sequence is critical because of constraint on M03
Path will always affect the project completion date DB0 duration changes from 15d to 20d (5 days longer) M04 completion date changes from 30 Oct to 4 Nov (5 days shifted) 2 1 1 2 Sample Schedule - Running on Scenario 1
may not affect the project completion date PC0 duration changes from 17d to 25d (8 days longer), but no impact to M04 completion M03 shifts, affecting negative total float (-8 days) to M02-PC0-M03 due to constraint use on M03 M02 > PC0 > M03 is now longest path since the gap between M03 to M04 has been used up 2 1 2 1 Sample Schedule - Running on Scenario 2
Near critical activities are activities that are close to becoming critical activities, It can be defined as: The terminology of “near to zero” may be different for every project, e.g. < 30d, <5% project duration Activity with total float near to zero Activity sequences that close to becoming longest path Activities sequence that is near to longest path It seems hard to determine near critical using CPM when the project approaches middle or final stage since almost all remaining works may be close to critical Expert opinions may be considered to determine its criticality regardless of the float value calculated Near critical based on expert judgement
Reasons why determining near critical activities is important: It can be surprising when the non-critical activities are becoming critical after the schedule updated. Identifying near critical activities at the earliest time can be the alarm for project teams to take any actions to maintain the schedule Managements often find difficulty in monitoring all activities other than critical ones. Near critical activities identification can be the navigator for managements to strongly focus on activities that may lead to project delay Management often put less attention to non-critical activities Critical activities may change as the project progressed
has a feature called “Calculate multiple float paths”, that is useful to identify the near critical activity by its float path 1 1 Feature can be accessed in Schedule Options Hit F9 > Options… > choose Advanced tab 2 2 Tick this to enable P6 calculating multiple float path 3 3 Choose the calculation method ▪ Total float : This will identify criticality by activity total float ▪ Free float : This will identify criticality based on longest path 4 5 4 Choose activity to set as end of float calculation, or leave it blank to calculate float based on project finish date/ constraint 5 Set the number of float path If 5 is entered, then it will calculate 5 most critical float paths ending with activity selected or project finish
multiple float path option is enabled, P6 will calculate Float Path and Float Path Order value Show these columns to see float path calculation Float Path : Group of activities based on its criticality, 1 means the most critical Float Path Order : Activity sequence order for each float path Schedule the project <F9> to re-calculate the float path value Notes ! Calculating multiple float path doesn’t affect how critical activities (Critical or Longest Path) are defined, it can be set separately through Schedule Options – General tab – Define critical activities as Sample Schedule
activities by Float Path, then Sort by Float Path Order to see the critical and near critical activities in sequential group and order Go to Group and Sort menu, and choose Float Path in Group By Sample Schedule
float path by Total Float will generate float path value based on activity total float Float Path Sequence 1 Critical A1 > A2 > A3 > XA Total float is 0 and also the longest 2 Near Critical-1 B1 > B2 > B3 Total float is 0 due to constraint use on B3 3 Near Critical-2 C1 > C2 Total float is 2 Sample Schedule – The smalles total float will be the most critical
float path by Free Float will generate float path value based on free float/ longest path 4d Sample Schedule – The closer an activity sequence to the longest path, the more critical it will be Float Path Sequence 1 Critical A1 > A2 > A3 > XA The longest path 2 Near Critical-1 C1 > C2 It has 2d gap before it becomes longest path 3 Near Critical-2 B1 > B2 > B3 It has 4d gap before it becomes longest path 2d
float path by Total Float with ending on B3 is limiting the float path calculation only to activities that linked to B3 Calculate multiple float path by Free Float will produce same result since there’s only one sequence linked to B3 Float Path Sequence 1 Critical A1 > B1 > B2 > B3 Sample Schedule – There’s only one sequence in Float Path, since no other activities linked to B3 Float paths are not calculated
critical activities reliability: Healthy project schedule tends to have reliable critical activities Check the schedule health Longest path (critical path) should have continuous activities sequence from project start or data date to the project completion Check longest path continuity The amount of delay for each activity on longest path/ critical path should be same with the delay on project completion Check longest path/ critical path integrity
to check Description Missing logic/ open end All activities shall have at least an FS/SS predecessor and an FS/FF successors Leads (negative lags) No lead (negative lags), convert lead to activity Lags Minimize lags, convert lag to activity Relationships Maximize FS logic, especially for critical sequences Hard constraint Minimize using hard constraint High total float Minimize activities with high total float, re-check the relationships Negative float No negative float, re-check the use of constraints High duration Most activity’s duration shall be less than the reporting period duration Link to WBS element All activities shall be linked to activity, not WBS element (not allowed in P6) DCMA 14-point assessment can be used for quantitative assessment guideline and basis
the activities in longest or critical path should be linked in FS sequences without any lag and constraints, so it will be easier to monitor the changes when schedule updated Some factors that may cause not continuous/ broken, 1. Use of constraint 2. Use of lag 3. Relationship from other project 4. Different calendar between activities
1. Use of Constraint It seems not logical when the schedule has no critical activities in the first 3 days Recommendation: Remove any constraints that can make longest path broken, even the use of constraints shall be as few possible in project schedule
2. Use of Lag Use of lag may cause difficulty in analyzing the longest path and sometimes lead to open-ended activities Recommendation: Convert lag to activity, even the use of lag should be avoided in project schedule open end
3. Relationship from other project When you link the activities between multiple projects, longest path may be broken Recommendation: All linked projects shall be opened simultaneously while calculating the float, and choose option to calculate float based on finish date of “Opened project” instead of “Each project” in schedule option
4. Different calendar between activities Non work period may be considered as floats when activities with different calendar are linked Non work period (5 d/week) Recommendation: Check carefully the sequence between activities with different calendars, adjust the duration if needed to make it unbroken
the number of delays in the longest path and project completion is not the same, then critical path integrity is doubtful Project duration is extended by 2 days after changing longest path activity duration by 2 days, it means the longest path has good integrity A2 duration changes from 3d to 5d Recommendation: Reassess schedule health and longest path continuity when the integrity check is failed
near critical activities properly can help the project team to prioritize the works and allocate the resources effectively Gather actual work information Update project schedule Assess critical-near critical activities Develop critical variance analysis Verify and plan the mitigation plan Collect all actual work information during reporting period for schedule updating Update the project schedule reflecting actual work achievement Assess the reliability of critical and near critical activities from scheduling view Record any update of critical activities and analyze its impact to project completion/ key milestones Verify critical activities to project teams and develop mitigation plan to maintain the schedule or to get the schedule back on track Monitor progress performance and mitigation plan execution Critical activities management process in each period
be planned when activities exceed the schedule threshold Total float after schedule update Condition Mitigation Plan/ Action > 10% PD - No need ≤ 10% PD - Close monitor < 5% PD Potential to become critical Plan preventive actions to maintain/ shorten the remaining duration to not becoming critical < 0 day Delays still can be mitigated without interrupting other divisions schedule Plan short term corrective action (e.g., 1~3 month look ahead) with more detailed target items to reduce delay impact < 0 day Delays still can be mitigated but interrupting other divisions schedule Plan short-long term corrective action with more detailed target items to reduce delay impact < 10% PD Delay mitigation need to change almost overall work sequences Plan recovery plan that may include change of execution plan to keep the completion date (re-baselining may be needed) PD: Project Duration Sample of Schedule Threshold Narrative
1: finish date delayed to 15 Oct 18 (6 days delay), resulting negative total float by -6d Sample Schedule – Update Period 1 ▪ Not-started activity remaining duration shall be maintained as same as baseline duration unless there is mitigation plan to shorten it 6 days delay
grouped by float path (using free float option) to monitor the critical sequences and prepare mitigation plan Sample Schedule – Update Period 1 – Group by Float Path 6 days delay Activities are completed, so it’s not considered as critical
simulated to the current schedule to clearly see its effort and result Sample Schedule – Update Period 1 – Group by Float Path – Simulation of Mitigation Plan 3 days acceleration 5 days acceleration ▪ Step-1 is mitigation plan that will be done in the next period ▪ Step-2 is next mitigation plan after step-1 mitigation plan succeeded, this will be adjusted based on the result of step-1 mitigation plan 3 days acceleration Step-1 Step-2
is excluded from current schedule update report since it will not be executed in current stage but still considered as next mitigation plan Sample Schedule – Update Period 1 – Group by Float Path – Simulation of Mitigation Plan w/o Step-2 ▪ Activities duration in mitigation plan step-2 shall be maintained as original since no corrective action is taken in current stage Step-1 Step-2 3 days acceleration 5 days acceleration
is described in critical variance analysis Sample Schedule – Update Period 1 – Critical Variance and Mitigation Plan Description Div. Float Path Total Float Current Target Cause Corrective Action Current Target Start Finish Start Finish STEP-1 Design Basis Design 1 -6d -3d 03-Sep-18 Actual 15-Sep-18 - 15-Sep-18 Late final study result Consolidation to close all issues: 14- Sep-18 Detail Design A Design 1 -6d -3d 16-Sep-18 30-Sep-18 16-Sep-18 27-Sep-18 Late design basis issuance Consolidation w/ client to speed up review: 24-Sep-18 Design B Design 2 -4d 1d 16-Sep-18 25-Sep-18 16-Sep-18 20-Sep-18 Late design basis issuance Issue clean document: 19-Sep-18 Install B Cons. 2 -4d 1d 26-Sep-18 13-Oct-18 21-Sep-18 08-Oct-18 Late design B finalization due to late design basis issuance Start soon after Design B Install C Cons. 3 3d 3d 14-Sep-18 06-Oct-18 14-Sep-18 06-Oct-18 Late design C receiving Start soon STEP-2 (future mitigation) Install A Cons. 1 -6d -3d 01-Oct-18 15-Oct-18 28-Sep-18 12-Oct-18 Late detail design A finalization due to late design basis issuance Construction steps will be studied in detail to shorten duration at least by 3 days Current schedule before mitigation Expected schedule after succeeding mitigation plan
in previous period shall be reviewed in order to prepare advanced mitigation plan (step-2) Sample Schedule – Update Period 2 – Review Previous Period Critical Variance and Target Description Div. Float Path Total Float Target Actual/ Forecast Status Remark Target Actual Start Finish Start Finish STEP-1 Design Basis Design 1 0d - 15-Sep-18 - 15-Sep-18 Actual Achieved Detail Design A Design 1 0d -4d 16-Sep-18 27-Sep-18 16-Sep-18 Actual 28-Sep-18 Forecast Not Achieved Design B Design 2 1d 1d 16-Sep-18 20-Sep-18 16-Sep-18 Actual 20-Sep-18 Actual Achieved Install B Cons. 2 1d 1d 21-Sep-18 08-Oct-18 21-Sep-18 Actual 06-Oct-18 Forecast Achieved Install C Cons. 3 3d 3d 14-Sep-18 06-Oct-18 14-Sep-18 Actual 05-Oct-18 Forecast Achieved STEP-2 (future mitigation) Install A Cons. 1 0d -4d 28-Sep-18 09-Oct-18 29-Sep-18 Forecast 10-Oct-18 Forecast Not Achieved Advanced mitigation plan shall be prepared Red : target was not achieved Green : target achieved
for period 2 Sample Schedule – Update Period 2 – Group by Float Path – Simulation of Mitigation Plan 4 days acceleration ▪ Install A need to be shortened by 4 days instead of 3 days as previously planned since predecessor is late from target
is detailed to monitor critical activities closer Sample Schedule – Update Period 2 – Group by Float Path – Simulation of Mitigation Plan Detailed Broken into 3 tasks ▪ If project scheduling rules do not allow new activities to be added to maintain baseline, then more detailed schedule can be developed in separate schedule
for next period Sample Schedule – Update Period 2 – Critical Variance and Mitigation Plan Description Div. Float Path Total Float Current Target Cause Corrective Action Current Target Start Finish Start Finish Detail Design A Design 1 -4d 0d 16-Sep-18 Actual 28-Sep-18 - 28-Sep-18 Late comment closing Accelerate final issuance Install A Cons. 1 -4d 0d 29-Sep-18 13-Oct-18 29-Sep-18 09-Oct-18 Late detail design A finalization Increase work resources and work in 2 shifts Detailed work steps are indicated in schedule Install B Cons. 2 3d 3d 21-Sep-18 Actual 06-Oct-18 - 06-Oct-18 Keep monitor Install C Cons/ 3 4d 4d 14-Sep-18 Actual 05-Oct-18 - 05-Oct-18 Keep monitor
project shall be clearly defined including its threshold in order to prepare enhanced mitigation plan Define Critical – Near Critical Activities 2 Reliable critical activity comes from reliable project schedule, therefore schedule shall be assessed in order to have healthy project schedule Assess Critical Activities Reliability 3 Mitigation plan for critical – near critical activities shall be planned and monitored to maintain project completion date on schedule Manage Critical – Near Critical Activities
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