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Change in critical path on conversion of programme from P6 to MSP

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Geetanjali Singh
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On conversion of P6 programme in MSP, there are more crtitical activities in msp programme in addition to the critical activities of P6 programme. Has anyone came across such situation?


What version of P6?

What version of MSP?

What type of transfer file? (mpx?, xml?)


Even after a perfect translation of the activity definitions, logic, calendars, and constraints - the number of tasks and the definition of "Critical" can be different in the two tools just based on your update status and calculation options.

First, "Longest Path" does not exist in MSP, so all "critical" flags are set based on Total Slack alone.

Second, WBS levels in P6 may be converted to summary tasks in MSP.  If you are simply counting "critical" tasks, the new summary tasks may be included in your count. 

Third, the schedule might be calculated differently:

  • MSP has no data date, so incomplete activities on a progressed schedule can be calculated very differently.
  • "Retained Logic" and "Progress Override" do not exist in MSP, which calculates the schedule similarly to the "Actual Dates" option in P6.
  • Relationship lags in MSP are always calculated according to the successor task calendar.  By default, P6 uses the predecessor calendar.
  • By default, tasks with late constraints in MSP will be allowed to to override predecessor logic to hold the constraint.

Finally, even if calculated dates are identical, Total Slack/Float might be calculated differently:

  • In the absence of progress or leveling, MSP Total Slack and P6 Total Float will be the same for non-summary tasks.
  • With resource leveling or progress, MSP Total Slack and P6 Total Float may be different for non-summary tasks.
  • For summary tasks (including group summary bars), MSP computes total slack based on the rolled-up early and late dates of the child tasks.  These values are meaningless and should not be compared with the corresponding group values in P6.
  • If "Calculate multiple critical paths" is selected (it's off by default), then MSP will set Total Slack for open-ended tasks to zero.