Bottlenecks Performance of most systems(at least before they are tuned)usually limited by performance of one or a few components:these are called bottlenecks E.g.80%of the code may take up 20%of time and 20%of code takes up 80%of time Worth spending most time on 20%of code that take 80%of time Bottlenecks may be in hardware(e.g.disks are very busy,CPU is idle),or in software Removing one bottleneck often exposes another De-bottlenecking consists of repeatedly finding bottlenecks,and removing them This is a heuristic 3 Database System Concepts,5th Ed. 23.3 @Silberschatz,Korth and SudarshanDatabase System Concepts, 5 23.3 ©Silberschatz, Korth and Sudarshan th Ed. 3 Bottlenecks Performance of most systems (at least before they are tuned) usually limited by performance of one or a few components: these are called bottlenecks E.g. 80% of the code may take up 20% of time and 20% of code takes up 80% of time  Worth spending most time on 20% of code that take 80% of time Bottlenecks may be in hardware (e.g. disks are very busy, CPU is idle), or in software Removing one bottleneck often exposes another De-bottlenecking consists of repeatedly finding bottlenecks, and removing them This is a heuristic