Difference between Retain Logic and Override Progress

Vladimir, You missed to mention that sometimes contractors were even doing construction works even without a plan or schedule (whether or not approved). And most of the time (again, if not all the time), contractors or specifically, site engineers and construction foremen do not or never follow an approved schedule or plan (and that's a reality as old as construction). Why? First, let me ask everyone (or all schedulers and planners), have you ever seen a construction foreman on site holding your approved schedule while executing the works? Well, for "resource constrained schedules", it is my opinion that a contractor with common sense or let's say smart enough would never intentionally delay a schedule, but shall certainly find ways to generate more profits from the works.

Anoon,

in resource-constrained schedules the choice of the wrong activity competing for the same resources may lead to large delays. We consider this out of sequence and insist on following the optimal order created by the scheduling tool.

Another case is starting the construction before the drawings were approved. This is risky but usual.

If out of initial sequence was analyzed and approved then it is fine. In other case it may create problems that can be avoided.

Apologies if I'm personally pissed-off with most (if not all) literatures pertaining to the subject / topic; and making mandatory recommendations presuming that they never make any mistake. Please let me challenge everyone of you to walk through your construction sites (assuming that you know all your planning & scheduling even without looking on print outs or your computer), and pin-point any out-of-sequence activity that you can see and penalize all your field personnel for not following your sequencing-logic (as planned). If you are able to see even one activity that you think is out-of-sequence, then for me, you have all the right to insist on using "Retained Logic" only in All Schedules! And punish all your field personnel and engineers as they are all stupid! Otherwise, if you know the Spanish term "Delicadeza", then I guess you already know what to do.

For me, the only difference between "Retained Logic" and "Progress Override" is misconception. "Retained logic" is just an illusion until realized. An illusion that is not corrected or rectified is stupidity or insanity. While "Progress Override" is just one of the tools or means to correct or rectify the schedule (if you know how to use it). Again, "Out-of-Sequence Activities" do not or never happen in actual construction (otherwise, all your site engineers, methods engineers and quality control engineers are stupid). Out-of-sequence activities only happen in your computer or on your schedule (or samples) which is just an illusion in the first place. Actual progress were based on facts!

f you use progess override it will do just that it will not honor the logic and it si possible that activities will be scheduled to be completed sooner than physcially possibel. i.e. I have an example that show drywall finishing PRIOR to stud which is physcially impossible. Also all float values will be incorrect. 

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Iyke,

How Retained Logic, Actual Dates, and Progress Override Deal With Out-Of-Sequence Progress

• Ultimately, it’s our recommendation that instead of relying on the Progress Override and Actual Dates options to deal with activities that progress out of sequence, owners should specify the use of the Retained Logic option and require contractors to address activities that progress out of sequence on an activity-by-activity basis as it occurs and to make appropriate changes to the schedule logic to ensure that the project schedule matches the current construction.

This is so true, a no-brainer broken logic can create all sort of schedule problems; unfortunately some owners might insist in hijacking your schedule and will not let you make changes in logic to your update schedules unless approved after a reluctant review.

• A revised Baseline once approved might represent an implicit change order but not so a schedule update. 
• Schedule updates are essentially informative and shall always represent your true plan; if there is out-of-sequence logic it is a faulty model that might create calculation errors. 
• If the update shows you are far from contract target(s) then the owner might require you to submit a recovery schedule.
• In no way the owner shall prevent you from having your plan.  You are the owner of the means and methods (unless it is a Construction Management Contract) . You have the right to make adjustments to your work plan as need be.
• Why this happens is a mystery to me, perhaps lack of understanding by the owner, perhaps it is because of claims paranoia, but it happens.

Best Regards,

Rafael

it is exactly as it states. Retained logic when an activity have started RETAINIED LOGIC IGNORES THE ACTUAL START DATE AND LOOKS AT THE REMAINING WORK OF THE PREDECESSOR AND WILL NOT PERMIT THE REMAINING WORK OF ITS SUCCESSOR TO BEGIN UNTIL THE PREDECESSOR HAS BEEN COMPLETED. 

If you use progess override it will do just that it will not honor the logic and it si possible that activities will be scheduled to be completed sooner than physcially possibel. i.e. I have an example that show drywall finishing PRIOR to stud which is physcially impossible. Also all float values will be incorrect. 

If you give me your email address I can send you my write up and example.