An interactive computer system at Anchor Anchovies has 70...

Name: Problem 2, Chapter 6: Probability, Statistics, and Queuing Theory with Computer Science Applications, Second Edition (Computer Science and Scientific Computing)
Uploaded: 2021-12-15T17:41:38-08:00
Duration: 1 min 7 s
Channel: Hast Aggarwal
Description: An interactive computer system at Anchor Anchovies has 70 active terminals with a mean think time of 30 seconds. The paging disk averages 5 accesses per interaction with the average access time of 0.05 seconds. The paging disk has an average utilization of 0.5 . What is the average system response time?

An interactive computer system at Anchor Anchovies has 70 active terminals with a mean think time of 30 seconds. The paging disk averages 5 accesses per interaction with the average access time of 0.05 seconds. The paging disk has an average utilization of 0.5 . What is the average system response time?

Key Concepts

Response Time Calculation

Response time is the duration taken by the system to complete a transaction from the user’s perspective. In closed queueing networks, it is determined by the relationship between the total number of users, throughput (derived from resource utilization and service demand), and the think time. It reflects not only the pure processing time but also any delays, making it a fundamental metric for evaluating interactive system performance.

Utilization Law

The utilization law connects the proportion of time a resource is busy (its utilization) with the system throughput and the service demand. It is used in performance analysis to determine throughput by dividing the resource utilization by the service demand, thereby linking resource performance with overall system behavior.

Think Time

Think time refers to the period during which a user interacts with the terminal and prepares a new transaction request after receiving a response. It is a key factor in interactive systems because it defines the delay between successive system requests, influencing the throughput and overall system performance when analyzed with other metrics such as response time.

Closed Queueing Networks

This concept models interactive computer systems with a fixed number of users, each alternating between thinking (or preparing a new request) and waiting for system responses. In such a network, the overall system performance is studied by considering the cyclic behavior of users, where the number of active jobs is constant and metrics like throughput and response time are derived using queuing theory formulas.

Service Demand

Service demand is the total processing time required by a system component to serve a customer or a transaction. In the context of the provided problem, service demand is calculated by multiplying the number of accesses by the average access time. It quantifies the load imposed on the system’s resources, such as a paging disk, during each transaction.

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