TOC – Critical chain I J.Skorkovský ESF-MU, KPH TOC concisely I (see PWP presentation about TOC) • origin: E.M.Goldratt, Jerusalem • cost world<->throughput world • analogy weight of the chain – solidity of the chain • how to find a bottleneck? • tools of TOC – tree structures • CRT – EC – TT – PT – FRT meaning: • Current Reality Tree - Evaporating Cloud Tree– Transition Tree - - Prerequisite Tree – Future Reality Tree TOC concisely I (see PWP presentation about TOC) • bottleneck in project management is critical path • finding (assessment) of bottleneck is not easy and often it is not explicit (uncompromising) • everybody knows something about TOC and nobody knows how to implement it to the real world- and this is again another bottleneck (tendon of Achilles from the heel to the scruff) TOC-five steps (revision) Five steps process: Step 0. Identify the Goal of the System/Organization Step 0.5 Establish a way to measure progress to Goal • Step 1. Identify the system’s constraint. • Step 2. Exploit the system’s constraint. • Step 3. Subordinate everything else to the above decision. • Step 4. Elevate the system’s constraint. • Step 5. If a constraint is broken (that is, relieved or improved), go back to Step 1. But don’t allow inertia to become a constraint. Linear image of the project • activities – abscissas – Gantt graph • constantly changing conditions (Parkinson low, Murphy low, Student syndrome, customer changes - „fancies “,“caprices“.. …. ), Parallel image of the project Project and its budget • price of the whole project • project length (time) • project stages and length of each activity • assigned resources to every activity and their capacities (time per defined period) • time reserves (buffers) and their estimation • unfavourable influences (see Murphy´s lows - http://murphy.euweb.cz, etc.) Selected Murphy´s laws • If your attack is going well, you have walked into an ambush. • Planner is alerted about modification of the plan exactly in the moment, when the plan is finally adjusted • To carry out n+1 trivialities you need two times more time than time necessary to carry out n trivialities (law 99 %) • If anything can go wrong, it will • Any given program, when running, is obsolete • No matter how many resources you have, it is never enough • Brains x Beauty x Availability = Constant. This constant is always zero. Project Pyramid - principle Example of the real budget- data is modified Capacity assignment Resources and orders Project environment is very complicated because of integration linkages and their dependencies Project environment is very complicated because of integration linkages and their dependencies The project must be protected against influences of breakdowns (troubles) Critical path, adjoining branches of the project and adjoining buffers (AB) Critical Path (CP) Critical Path (CP) • Critical Path Method, abbreviated CPM, or Critical Path Analysis, is a mathematically based algorithm for scheduling a set of project activities. It is an important tool for effective project management. Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Critical Path (CP) Multi-project Management Multitasking characterization • people always overestimate the length of their tasks • salesman offers impracticable terms (dates) • The fight for reserves (capacities) causes, that all saved time is fully wasted (Student´s syndrome) • Reserves (if any) are used badly • Bad use of reserves causes lack of transparent assignment • Non transparent priorities are parents of bad multitasking • Bad multitasking causes longer duration of all activities (tasks) and thus all the projects CP definition (more in detail) Critical chain definition In TOC the Critical chain is defined as the longest way (meaning time) from the starting point of the project graph (Gantt) to the ending point which takes into account technological dependencies as well as time of the tasks and moreover, capacities of assigned resources. With infinite capacities of resources you can consider Critical path=Critical chain Multi-project management and critical resources (CCR) used in more that one project branch Multi-project management and critical resources (CCR) used in more that one project branch Project management based on remainimg time in buffers – Buffer Management • Buffers are used for timely warning and that is to say predicting and avoiding future problems related to project deadlines (milestones) • It is also used as a guideline for corrective actions Basic metrics showing the project status • The partial size of Critical chain (CC) fulfilled in days (in %) • How much of buffer size was used to fulfil above mentioned partial size of CC ? • Trend of project (buffer consumption graph- see next slide) • Consumption of the financial buffer • Priorities – bigger buffer penetration- bigger priority • Adjoining branches have always lower priorities • It is not allowed to create bad multitasking Trends of the project Project Quick, resources A-E and activities X,Z,X,W, and V Time distribution Five projects and modifications • If we consider for every activity time buffer 8 days we will get : Five projects and modifications (added buffers) and four types of troubles Five projects after modification (buffers united to one and placed to the end of the project) Critical path- Critical chain Gantt graph for X,Z,V,W a Z Critical chain with buffers Multitasking – sequential order of resources Matrix scheme Collisions among project and department managers (Mi) (those who control resources) Collisions among project and department managers (Mi) (those who control resources) • The synchronization of the starts of the projects is based on most utilized (overloaded resource which is the cause of prevailing quantity of conflicts • The above mention statement means, that all your started projects are covered by all most critical resources (CCR) of the organization and due to this fact you will have less started projects. • Less started projects results in less quantity of conflicts among project managers and department managers Multitasking – modified schedule-stage 1 Collisions among project and department managers (Mi) (those who control resources) • To all three projects we have inserted buffers protecting the critical chain • On the other hand, after reshuffling of the schedule in order to decrease quantity of conflicts we did nothing to protect critical resource (drum, CCR) • Above mentioned statement is the reason to insert additional protecting buffer before drum resource (Drum-Feeding Buffer) = DFB = Multitasking – modified schedule-stage 2 Buffer consumption - variant A Priorities assigned to resources • If one resource have to be assigned to two activities starting in the same moment so the first activity which will start is the one belonging to the project with bigger project buffer penetration • If none of all project buffers were penetrated with previous activities, so the first starts this activity which belongs to the critical chain. Priorities assigned to resources Main benefits of the Critical Chain (CC) usage • Every single project ends significantly earlier, than projects where other project management methods than CC were applied • Total time needed to end more project than one is markedly shorter • Promised delivery times are fulfilled with higher rate of credibility • You will have more free capacity of all used resources Main benefits of the Critical Chain (CC) usage • Better initial estimation about project timing and thus bore accurate planning • During starting of the projects you did not meet any problem taking into consideration drum resource • Decrease of unfavourable effects such as Student syndrome, Murphy attacks and impacts of Parkinson´s laws by redeployment and integration of all buffers to one and only one project buffer at the end of the project • Utilization of benefits caused by earlier ended activities • Use of reporting system which provides you with valuable information of buffer penetration , the extent of time reserves and thus better helping system for assigning priorities