According to Goldratt (1990a), TOC initially recognizes that every organization must be understood as a system with a goal; hence, every action taken by any part of the system must be judged by its impact on that goal. It is imperative to define measures that allow for the evaluation of the impact of any subsystem, and of any local action in this subsystem. A system constraint must be defined as anything that significantly prevents a system from improving its performance towards that goal. Every system must present at least one constraint. In addition, there will always be very few constraints, since there is always a single weaker link in a chain (Goldratt, 1990b Prema Goldratt-u (1990a), TOC u početku prepoznaje da svaka organizacija mora biti shvaćena kao sistem sa ciljem, stoga se svakoj akciji, koja postaje deo sistema mora suditi po njenom uticaju na taj cilj. Imperativ je da se definišu mere koje omogućavaju procenu uticaja bilo kog podsistema, kao i bilo koje lokalne akcije u nekom podsistemu. Sistem ograničenja mora biti definisan kao nešto što značajno sprečava sistem u unapređivanju performansi ka tom cilju. U svakom sistemu mora biti prisutna najmanje jedna prepreka. Pored toga, uvek će biti malo ograničenja, jer uvek postoji jedna slabija karika u lancu (Goldratt, 1990b). The constraint may be physical, such as a machine with limited capacity, a policy or a behavior constraint. Policy constraints often arise when the company environment changes while its policies remain unchanged. Most significantly, policy constraints are usually under the control of the organization’s management (Mabin and Balderstone, 2003). Ograničenja mogu biti fizička, kao što je mašina sa ograničenim kapacitetom, politikom ili ponašanja ograničenja. Ograničenja zbog politike se često javljaju kada kompanija menja ambijent poslovanja , dok politika poslovanja ostaje nepromenjena. Što je još značajnije, Ograničenja zbog politike su obično pod kontrolom menadžmenta organizacije (Mabin i Balderstone, 2003). Goldratt (2004) asserts that the goal of a capitalist enterprise is to make money in both the present and the future, and that this must be evaluated in terms of its net profits (NP) and return on investment (ROI). To judge the impact of a local action on NP and ROI, TOC uses three performance measures (Corbett, 1998): Goldratt (2004) tvrdi da je cilj kapitalističkog preduzeća da se novac zarađuje i u sadašnjosti i u budućnosti i to mora biti ocenjivano u odnosu na neto profit (NP), i u odnosu na povratak investicija (ROI). Da bi ocenili uticaj lokalne akcije na NP i povraćaj ulaganja, TOC koristi tri načina merenja (Korbet, 1998): (1)Throughput (T): revenue minus total variable costs (TVC). TVC is the cost that varies for every extra unit produced (such as raw material) and does not include direct (unless they are paid by piece) or indirect labor costs. All other costs are included in the OTerating expense (OE) category. The throughput will tell us how much money the company generates with the sale of one unit of the product (1) protok- prOTusna moć (proizvodnja) (T): prihodi minus ukupni varijabilni troškovi (TVC). TVC je cena koja varira za svaku dodatnu jedinicu proizvodnje (kao što je sirovina) i ne obuhvata direktne (osim ako su plaćeni po komadu) ili indirektne troškove rada. Svi drugi troškovi su uključeni u kategoriju OTerativnih troškova (OE). PrOTusna moć će nam reći koliko novca kompanija ostvaruje sa prodajom jedne jedinice proizvoda. (2)Investment (I): all the money captured by the system. (3)OE: all the money that the system spends transforming investments into throughput. 2) Investicije (I): sav novac zarobljen od strane sistema. (3) OT-OTetativni troškovi: sav novac koji sistem troši transformišući ulaganja u proizvodnju. TOC suggests five focus steps that must be followed to ensure effective ongoing TOC improvements (Goldratt, 2004): TOC predlaže fokusiranje na pet koraka koja se moraju slediti da bi se obezbedila efikasnost u poboljšanjima TOC-a. (Goldratt, 2004): (1)Identify the system constraint(s). (2)Decide how to exploit the system constraint(s), i.e. increase the system throughput, completely eliminating any kind of waste in the system constraint. (3)Subordinate everything else to that decision. This implies ensuring that all the other elements of the system work towards exploiting the constraint, which should be evaluated according to how well they achieve that objective. (4)Elevate the system constraint(s), i.e. increase the system throughput by increasing the investment volume towards the constraint, e.g. by investing in new market segments to elevate a market constraint. (5)If a constraint was broken in a previous step, return to the first step, but prevent inertia from becoming the system constraint. (1) Utvrditi sistem ograničenja (a). (2) odlučiti kako upotrebiti ograničenja(e), npr. povećati prOTusnu moć sistema, koji u potpunosti eliminiše gubitke u sistemu ograničenja. (3) podređivati sve ostalo na osnovu te odluku. Ovo podrazumeva da treba obezbediti da svi ostali elementi sistema rade na eksploataciji ograničenja, koji treba da se ocenjuju prema tome koliko su dobro postigli taj cilj. (4) unaprediti sistem ograničenja, odnosno poboljšati prOTusnu moć sistema povećanjem obim investicija u pravcu ograničenja, npr. ulaganjem u nove tržišne segmente da bi se podiglo ograničenje tržišta. (5) Ako je ograničenje prekinuto u prethodnom koraku, treba se vratiti na prvi korak, ali sprečiti da inercija postane sistema ograničenja. The TOC methodology for outbound logistics is a direct application of these steps, as will be discussed in section 4. An important aspect of the TOC steps is their orientation towards improvement efforts. TOC, unlike many continuous improvement initiatives intended to reduce OE and which by its inherent nature would be limited (Larsson et al., 2008), it makes more sense to focus improvement efforts on increasing Throughput as means of improving the global financial performance. Throughput orientation is a direct effect of the five steps described above and is supported by the use of performance measurement systems that facilitate throughput maximization through management of constraints (Boyd and Gupta, 2004). The TOC approach for outbound logistics has a definite throughput orientation, which challenges some of the premises often associated with practices aimed primarily at local Optimizations and at the reduction of logistics costs. These assumptions are discussed below. Metodologija TOC-a u spoljnjoj logistici je direktna primena ovih koraka, koji će biti detaljnije razmotreni u odeljku 4. Važan aspekt TOC koraka je njihova orijentacija ka unapređenju. TOC za razliku od mnogih kontinuirano poboljšava inicijative koje su namenjene smanjenju OT-a i koje će po svojoj prirodi biti ograničene (Larson et al, 2008.), te je bolje da se fokusira na povećanje napora u poboljšanju propusne moci kao sredstvo za poboljšanje globalnih finansijskih performansi. Orijentacija na produktivnost je direktan efekat jednog od gore opisanih pet koraka, i podržava korišćenje sistema merenja performansi koji olakšavaju maksimizaciju protoka kroz upravljanje ograničenjima (BoJd i Gupta, 2004). TOC pristup za spoljnju logistiku ima jasnu propusnu orijentaciju, koji osporava neke ranije pomenute tačke često povezivane sa praksom koja je prvenstveno usmerena na lokalnu optimizaciju i na smanjenje troškova logistike. Ove pretpostavke su u daljem tekstu. 3. Some assumptions challenged by TOC TOC challenges some implicit or explicit premises about SCM and logistics practices that users and academicians often take for granted. Because of their important implications, each of these assumptions is presented and discussed according to the TOC perspective 3. Neke pretpostavke osporavane teorijom ograničenja TOC izaziva neke implicitne ili eksplicitne premise o SCM i logističkim praksama koje korisnici i akademici često uzimaju zdravo za gotovo. Zbog svoje važne implikacije, svaka od tih pretpostavki je predstavljena i razmotrena u skladu sa TOC. 3.1 Supply chain (SC) performance measures failed According to Holmberg (2000) and Beamon (1999), SC performance measures are often an extension of ‘‘traditional’’ company indicators. Neely et al. (1995) claimed that a systemic approach and generic application of SC performance measures have not yet been created for that purpose. Beamon (1999) and Holmberg (2000) agree that there is no connection or compatibility between SC performance measures and SC strategies. 3,1 Lanac snabdevanja (SC), mere performansi (načini merenja) su pogresni Prema Holmberg (2000) i Bimon (1999), mere performansi lanca snabdevanja su često produžetak ''tradicionalnih'' pokazatelja kompanije. Neeli i saradnici (1995) su tvrdili da sistemski pristup i generička primena mere performansi LS nisu stvorene za tu namenu. Bimon (1999) i Holmberg (2000) slažu se da ne postoji veza između LS i kompatibilnosti mere performansi i strategije LS. Traditional approaches for SC performance measures fail when they assume that if each chain member is managed as a separate entity and its is performance maximized, the benefits of the chain as a whole will also be maximized. A typical problem in SCM is that the system of measures seeks to OTtimize the performance of individual processes. In fact, many performance measurement systems evaluate the performance of a link in the chain as a function of how well it met the needs of its immediate client, instead of the SC’s end consumer. Another problem lies in the fact that each link eventually has its own system of measures, leading to a dysfunctional behavior (Watson and Polito, 2003). Tradicionalni pristupi u merenju performansi LS podbaci kada pretpostave da se svakim članom lanca upravlja kao posebnim entitetom i njegovim uvećanim performansama, gde će korist od lanca u celini takođe biti uvećana. Tipičan problem u SCM je da sistem mera nastoji da optimizuje performanse pojedinačnih procesa. U stvari, mnogi sistemi za merenje performansi ocenjuju učinak karike u lancu, kao funkcije koliko je dobro ispunila potrebe svojih neposrednih klijenata, umesto krajnjeg potrošača u LS. Drugi problem leži u činjenici da svaka karika eventualno ima sopstveni sistem mera, što dovodi do nefunkcionalnog ponašanja (Votson i Polito, 2003). According to Goldratt and Goldratt (2007), from a company perspective, when there is a conflict between a local OTtimum (sector performance) and a global Optimum (company performance), the local OTtimum should be discarded. However, such is not the case in a SC composed of several business units. When there is conflict between a local OTtimum (business unit performance) and a global OTtimum (SC performance), neither the local nor the global OTtimum should be discarded (Goldratt and Goldratt, 2007). Figure 1 illustrates this conflict from the standpoint of a business unit inserted in an SC. Prema Goldratt i Goldratt (2007), iz perspektive kompanije, kada postoji konflikt između lokalnog optimuma (sektor rada) i globalnog optimuma (performanse preduzeća), lokalni treba odbaciti. Međutim, nije takav slučaj u LS, koji je sastavljen od više poslovnih jedinica. Kada postoji konflikt između lokalnog optimuma (performanse poslovne jedinice) i globalnog optimuma (performansi LS), ni jedan ni drugi ne treba da budu odbačeni (Goldratt i Goldratt, 2007). Slika 1 ilustruje ovaj sukob sa stanovišta ubačene poslovne jedinice u LS. Conflicts between local and global OTtima in a company are strong evidence that incorrect performance measures are being used to evaluate each area. Moreover, conflicts between local and global OTtima in an SC are strong evidence that the rules that govern the business relationships between the companies are erroneous. Therefore, new rules are needed to enable companies to work together to eliminate such conflicts (Goldratt and Goldratt, 2007). Sukobi između lokalnog i globalnog optimuma u firmi predstavljaju dokaze da se netačne mere performansi koriste za procenu svake oblasti. Štaviše, sukobi između lokalnog i globalnog optimuma u LS su jaki dokazi da su pravila koja se koriste u upravljaju poslovnim odnosima između kompanija pogrešna. Dakle, nova pravila su potrebna da se omogući preduzećima da rade zajedno kako bi se izbegli takvi konflikti (Goldratt i Goldratt, 2007). To eliminate this conflict, a fundamental question that each link should ask itself is (Goldratt and Goldratt, 2007): at what moment does a sale occurs? Usually, each SC member focuses decisions on maximizing sales from immediate downstream partners (myOTic revenue), and minimizing (myOTic) costs from the relationship with its immediate upstream partners (Simatupang et al., 2004). The source of the so-called myopic revenue is payment transfer from the exchange of stocks between trading partners, since a stock transaction between SC members is considered a sale. The result is that each member tends to reason within organizational boundaries, instead of considering the SC as a whole. Each company improves its own revenue, ignoring the impact of its actions on the other SC links. Therefore, maximization of individual performance often takes place at the expense of the overall SC performance, and maximization of the SC performance as a whole is usually not attained (Simatupang et al., 2004). Da bi se uklonio ovaj sukob, osnovno pitanje koje svaka karika treba sebi da postavi je (Goldratt i Goldratt, 2007): U kom momentu se javlja prodaja? Obično, svaki član LS fokusira odluke o maksimiziranju prodaje od neposrednih kasnijih partnera (kratkovidi prihoda), i minimiziranja (kratkovidi) troškova iz odnosa sa svojim neposrednim prethodnim partnerima (Simatupang et al, 2004.). Izvor tzv kratkovidi prihoda plaćanja Transfer od razmene akciJa između trgovinskih partnera, Jer se akciJa transakciJe između članova SB smatra prodaJom. Rezultat Je da svaki član ima tendenciJu da rezonuje unutar organizacije, umesto razmatranja bezbednosti u celini. Svaka kompaniJa poboljšava sOTstvenih prihoda, ignorišući uticaJ svoJih aktivnosti na druge SB veza. Dakle, maksimizaciJa individualnih performansi često se odviJa na štetu ukupne bezbednosti performansama, i maksimizaciJu SB performanse kao celini se obično ne postiže (Simatupang et al, 2004.). According to TOC, a sale should only be acknowledged when the final SC customer has concluded the purchase (Goldratt and Goldratt, 2007). At that moment, the money paid should be distributed among the links of the chain participating in the supply of the sold item. While the links of an SC continue to believe that a sale took place only when there was a transaction of goods between links, the synchronization and coOTerative efforts in the SC will be blocked. Besides the fact that they do not lead to real coOTeration among the members of the SC, a significantly undesirable effect of the use of measures aimed at maximizing the performance of each link in the SC is that they encourage the pushing of stock along the SC. This subject is the next tOTic of discussion. A different system of measurement prOTosed by TOC is presented in section 4. Prema TOC-u, prodaja treba da bude priznata, kada je krajnji kupac u LS rešio izvršiti kupovinu (Goldratt i Goldratt, 2007). U tom trenutku, novac bi trebalo da bude podeljen između učesnika u lancu snabdevanja. Dok učesnici u LS i dalje veruju da se prodaja desila tek kada je došlo do razmene robe između učesnika u LS, sinhronizacija i napori u koOTeraciji LS će biti blokirani. Pored činjenice da oni ne dovode do stvarne saradnje među učesnicima u LS, znatno nepoželjan efekat upotrebe mera usmerene ka maksimiziranju performansi svake karike u LS je taj da one podstiču gurani tok duž LS. O ovome se rapravlja u sledećoj diskusiji. Drugačiji sistem merenja performasi koji je predložio TOC dat je u odeljku 4. 3.2 The pushing stock practice If a sale is considered concluded when goods are transferred to the upstream link there is a clear tendency for each link to push stock downstream in the SC. Manufacturers under pressure to come up with ideal solutions, usually aimed at reducing costs, tend to push their products to the distribution channels as soon as they are manufactured. The distributor, in turn, is then strongly motivated to push his stocks along the SC downstream to improve his stock turnover performance. Thus, supplier, manufacturer, distributor and each additional SC link strive to push stock until it arrives at the store and/or the end consumer (Kendall, 2005). 3,2 guranje akciJa praksa Ukoliko se prodaja smatra zaključenom kada se roba pebaci na prethodnu vezu tamo Je Jasna tendenciJa za svaki link da kasnije pomera akciJe u LS. Proizvođači pod pritiskom da dođu do idealnih rešenja, obično u cilju smanjenja troškova, imaju tendenciju da guraju svoje proizvode u kanala distribucije čim su proizvedeni. Distributer, za uzvrat, je snažno motivisan da gura svoje rezerve duž LS nizvodno kako bi pOTravio svoj promet. Dakle, dobavljač, proizvođač, distributer i svaki drugi učesnik u LS nastoji da gura rezerve proizvoda dok ne stignu u prodavnicu i / ili krajnjem potrošaču (Kendal, 2005) There is also a marketing reason for such behavior. Many products have a shorter customer tolerance time than replenishment time, requiring them to be available on store shelves for immediate purchase. The general practice of chain members is therefore to keep products as near as possible to final customers, usually at the retail level. This is a typical downstream product push behavior aimed at increasing consumption. However, the push behavior requires a good forecasting model to predict where and when stocks will be needed (Goldratt and Goldratt, 2007; Schragenheim, 2007a). There is a narrow correlation between forecasting, batching and the practice of pushing stock. Far-future forecasting encourages production planners to schedule large batches. The supposed knowledge of requirements (from the forecast) in the future, storage space for large stocks and pressure for efficiency and low costs lead to larger than necessary batches (Schragenheim and Burkhard, 2007). Despite sOThisticated forecasting systems and high stock levels, shortages occur regularly. Regardless of how good the forecasting mechanism is, it cannot really predict the actual demand (Schragenheim, 2007a). Tu je i marketinški razlog za takvo ponašanje. Mnogi proizvodi imaju kraću toleranciju kupca od vremena za dopunu , zahtevajući da oni budu dostupni na policama prodavnica za kupovinu odmah. Opšta praksa učesnika u lancu snadbevanja stoga je da proizvodi budu što bliže krajnjim korisnicima, obično na nivou malOTrodaje. Ovo je tipično guranje kasnijeg proizvoda u cilju povećanja potrošnje. Međutim, pritisak ponašanja zahteva dobar model za prognoziranje gde i kada će biti potrebno dopunjavanje zaliha (Goldratt i Goldratt, 2007; Schragenheim, 2007a). Postoji uska veza između predviđanja, tražnje i prakse guranog toka. Dugoročne prognoze omogućavaju planiranje serijske proizvodnje. Navodno znanje o zahtevima u budućnosti, skladišni prostor za velike zalihe i zahtev za efikasnost i niske troškove dovešće do većih serija nego što je potrebno (Schragenheim i Burkhard, 2007). Uprkos sofisticiranih sistema predviđanje i visokog nivoa zaliha, nestašice se javljaju redovno. Bez obzira na to koliko je dobar mehanizam prognoziranja, ne može se predvideti stvarna potražnja (Schragenheim, 2007a). Goldratt and Goldratt (2007) defend that the batch practice, usually stimulated by efficiency measurements, significantly inflates replenishing time, thereby inflating the required stock level along the SC. They define replenishing time as the sum of three types of lead times: order lead time (OLT), production lead time (PLT) and transportation lead time (TLT) (further discussed in section 4). The effects of the batch practice on these lead times are: Goldratt i Goldratt (2007) koji brane serijsku proizvodnju, obično podstaknutu efikasnim merenjem, značajno podiže vreme pOTunjavanje, čime podiže potreban nivo zaliha uz LS. Oni definišu vreme dopunjavanja kao zbir tri vrste vremena: vreme porucivanja (OLT), vreme proizvodnje (PLT) i vreme transporta (TLT) (detaljnije razmotreno u odeljku 4). Efekti seriJske proizvodnje su: batch practice – serijska proizvodnja Shortages and surpluses are undesirable effects common to the practice of pushing products along the SC, with negative consequences on sales due not only to the unavailability of the product at the point of sale, but also to the need to deal with excess inventories. The elimination of these undesirable effects must necessarily involve the elimination of the practice of pushing products in the SC. Nestašice i viškovi su nepoželjni efekti u praksi guranih proizvoda duž lanca snadbevanja, sa negativnim posledicama na prodaju ne samo zbog nedostupnosti proizvoda na mestu prodaje, ali i potrebu da se bave viškom zaliha. Otklanjanje ovih neželjenih efekata mora nužno da podrazumeva eliminisanje prakse guranih proizvoda u LS. 4. The TOC pull distribution methodology There is a conflict in distribution environments that blocks the maximization of their performance, driving managers and decision makers into a trade-off between ensuring the availability of products to the end consumer while simultaneously reducing the logistics costs of these distribution systems (Goldratt and Goldratt, 2007). Figure 2 illustrates this conflict. 4. TOC u metodologiji vucene distribucijePostoji sukob u distribuciji okruženja koja blokira maksimiziranje njihovog učinka,upravljanje menadžerima i donosiocima odluka u trade-off da obezbedi dostupnost proizvoda krajnjem potrošaču uz istovremeno smanjenje troškova logistike ovih distributivnih sistema (Goldratt i Goldratt, 2007). Slika 2 ilustruJe ovaJ sukob. The solution usually adOTted to deal with the conflict is to find a compromise between conflicting needs, often through mathematical modeling based on the costs associated with each side of the conflict for later identification of the OTtimal point that would minimize these costs. Calculations of economic order quantity (EOQ), with the consequent use of larger lots than strictly necessary and their related effects, reflect this way of thinking. Another typical consequence of living with this conflict is the constant search for better ways to predict demand, so that OTtimal inventory levels are maintained at each site and for each product. Rešenje je da se obično pronađe kompromis između sukobljenih potreba, često kroz matematičko modeliranje na osnovu troškova koji su u vezi sa svim stranama u konfliktu zbog kasnije identifikacije OTtimalne tačke koje bi minimizirale te troškove. Izračunavanje kolicine ekonomskog poretka (EOK), sa posledicnim korišćenjem većih parcela od striktno neOThodnih i odgovaraJućih efekata, odražavaJu taJ način razmišljanja. Druga tipična posledica ovog konflikta je konstantna potraga za boljim načinima da se predvidi potražnja, tako da se OTtimalni nivo zaliha vodi na svakoj lokaciji i za svaki proizvod. Whenever a conflict leads to a bad compromise (such as undesirable levels of lost sales resulting from shortages allied to low inventory turns), efforts should be made to break the conflict, identifying one or more erroneous assumptions that help perpetuate the conflict (Goldratt, 2008). The TOC approach presented in this section challenges the assumption that the best way to manage distribution systems is by replacing stock as a function of forecasted sales. As will be better demonstrated later in this section, the TOC pull replenishment solution exploits the fact that the accuracy of the forecast depends on the stage (retails, regional warehouse (RWH), central warehouse (CWH), etc.) of the distribution system (Yuan et al., 2003). Svaki put kad konflikt vodi ka lošem kompromisu(kao što su neželjeni nivoi usled lose prodaje koja je rezultirana nestasicom i losim pOTisom ), treba preduzeti napore da se on prekine, identifikovanjem jedne ili više pogrešnih pretpostavki koje pomažu da se i sam ovekoveci (Goldratt, 2008 .) Pristup TOC predstavljen u ovom odeljku izaziva pretpostavku da Je naJbolji način za upravljanje sistemom distribucije zamena akciJa kao funkciJa prognozirane prodaJe. Kao što će biti bolje prikazano kasniJe u ovom odeljku, TOC vuce pOTunjena rešenje eksploatisuci činjenicu da tačnost prognoze zavisi (prodaje, regionalna skladišta (RVH), centralni magacina (CVH), itd) od sistema distribuciJe (Juan et al, 2003). ..

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