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xTuple for Service Businesses Demo Guide |
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xTuple for Service Businesses Demo Guide |
| 2. Definitions | ||
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 | Chapter 4. Constraint Management |  |
What is a buffer? In short, a buffer is a little extra of something that we maintain to ensure we can handle unexpected fluctuations. xTuple ERP's constraint management system reports on three types of buffers: stock, time, and capacity. The following examples from daily life may help explain the three different kinds of buffers:
A stock buffer is like the extra coffee we keep in the cupboard to make certain we have enough should company drop in. For example, let's say we want to always keep at least three pounds of coffee on hand. Three pounds, then, is our buffer quantity. As long as we have this buffer, we're confident we'll have enough to serve unexpected guests. Whenever our supply drops below three pounds, we'll put coffee on our shopping list and buy more. Just because the coffee falls below three pounds doesn't mean we're in a critical situation. However, if we fall significantly below that level, we need to act immediately.
A time buffer is like the time we factor into a trip to the airport to catch a flight. Let's say we allow ourselves three hours to reach the airport, check bags, pass through security and proceed to the gate ready to board. That means our time buffer is three hours. If we get stuck in traffic for two hours, then we've used up 66% of our buffer. This is now a critical situation requiring our full attention. We must act immediately to either get out of traffic, take an alternate route, or reschedule our flight.
A capacity buffer is like the surface on your barbecue grill which can hold up to 12 hamburgers at one time. In this scenario, the grill's capacity buffer is 12. If each hamburger takes 15 minutes to cook—and you can cook 12 at a time—then you can produce 48 hamburgers in an hour. Now, let's say you've got 100 guests coming for dinner. If your plan is to feed everyone in one hour, you've got a capacity problem. You'll either need to fire up an extra grill, or start cooking an hour early to build up your stock burger buffer ahead of time.
The critical buffer status in the xTuple ERP constraint management system is 66%. In other words, any time we consume 66% of a buffer, then it's time to act immediately to resolve the situation. Using the coffee example, if our supply drops to one pound (and our buffer quantity is three pounds), then we've used up two-thirds of our buffer—or 66%. With that much of our buffer consumed, we need to buy more coffee right away. The 66% value is a percentage that is widely used in academic research and practical real-world implementations of the Theory of Constraints—a theory pioneered by Eliyahu Goldratt.
Now that we have gained a basic understanding of the different buffer types, we can begin to look at how these buffers function in xTuple ERP.
The scenarios described in this section refer to items and other data found in the xTuple ERP demo database. The demo database is available for download from the xTuple website—or online as a hosted demo.
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| 1. Overview |  | 3. Stock Buffer Scenario |