Open Lines with Finite Buffers - Principles

Open lines with buffers are very similar to open lines with no buffer restriction, except that finite buffers impose additional constraints on their performance. Therefore, the principles of open lines with infinite buffer generally apply to lines with buffers.  However, we also have some additional principles related to buffering.  These are very similar to the buffering principles of closed system with finite buffers.  The only difference is that in a closed system WIP is fixed, so that altering buffers affects throughput gets affected by the buffer, while in the open case throughput is fixed so altering buffers only affects WIP level.

• Principle (Minimum Buffer): In an open system for a given release rate there exists a minimum buffer size (may be zero) below which the line becomes unstable.

 
• Principle (Buffering): The WIP level of an open line is a non-increasing function of the buffer size.

 
• Principle (Diminishing Return to Buffering): The decrease in line WIP level from adding a unit of buffer space at a station in an open line decreases as the size of the buffer increases.

 
• Principle (Buffer Position): If all non-bottleneck machines are identical and all buffers are of equal size, then the decrease in line WIP level from adding an additional buffer space will be largest either directly before or after the bottleneck station.

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