A matrix-geometric solution for the multiserver nonpreemptive priority queueing model with mixed priorities.

This paper describes the analysis of multiserver queues with nonpreemptive mixed priorities. Such priority structures occur, for example, in initiator settings within the mainframe operating system MVS: job classes have to be assigned to initiators and their priorities may differ amongst the initiators. Results of the analysis provide insight in how average queue lengths in this priority system behave under different class loads. Bounds have to be defined in order to obtain a matrix-geometric solution and it is shown how this affects the average queue lengths. The results should eventually allow to derive guidelines with respect to initiator definitions.Model; Models;

Activity Based Costing techniques for workload characterization.

This paper addresses the problem of non-captured service demands in workload monitoring data. Capture ratios are the coefficients that correct the workload service demands so that they fit the global system monitoring data. This paper proposes new techniques for the determination of capture ratios by means of Activity Based Costing techniques. The techniques are illustrated by means of a case study, which also illustrates the non-trivial nature of capture ratios in practical performance analysis.Activity based costing;

Queue lengths and waiting times in the two-class two-server queue with nonpreemptive heterogeneous priority structures.

Our aim is to analyze a multiserver queue with nonpreemptive heterogeneous priority structures, which arises in the performance evaluation of batch initiator settings n MVS. We use matrix-geometric methods and derive the stationary distribution of queue lenghts and waitng times for the Markovian two-class two-server case.Structure; Performance; Performance evaluation; Evaluation; Methods; Distribution;

Grosch's law: a statistical illusion?.

In this paper a central law on economies of scale in computer hardware pricing, Grosch's law is discussed. The history and various validation efforts are examined in detail. It is shown how the last set of validations during the eighties may be interpreted as a statistical misinterpretation, although this effect may have been present in all validation attempts, including the earliest ones. Simulation experiments reveal that constant returns to scale in combination with decreasing computer prices may give the illusion of Grosch's law when performing regression models against computer prices over many years. The paper also shows how the appropriate definition of computer capacity, and in particular Kleinrock's power definition, plays a central role in economies of scale for computer prices.Law;

On closed queueing networks with mixed preemptive resume priority servers.

This paper discusses a typical closed queueing network model in which multiple preemptive resume servers are present with different priority structures at each priority node. An algorithm is developed that is applicable for the three-node two-class model and results are compared to point estimates obtained from simulation. The algorithm is partly based on the Delay/MVA algorithm developed by Bondi and Chuang, because of the accuracy with which instant arrival queue lengths at fcfs servers are calculated. Results are also compared with results obtained from the Shadow Approximation.Networks;

Provalble bounds for the mean queue lenght in a heterogeneous priority queue

status: publishe

Activity Based Costing techniques for workload characterization

This paper addresses the problem of non-captured service demands in workload monitoring data. Capture ratios are the coefficients that correct the workload service demands so that they fit the global system monitoring data. This paper proposes new techniques for the determination of capture ratios by means of Activity Based Costing techniques. The techniques are illustrated by means of a case study, which also illustrates the non-trivial nature of capture ratios in practical performance analysis.status: publishe

Grosch's law: a statistical illusion?

In this paper a central law on economies of scale in computer hardware pricing, Grosch's law is discussed. The history and various validation efforts are examined in detail. It is shown how the last set of validations during the eighties may be interpreted as a statistical misinterpretation, although this effect may have been present in all validation attempts, including the earliest ones. Simulation experiments reveal that constant returns to scale in combination with decreasing computer prices may give the illusion of Grosch's law when performing regression models against computer prices over many years. The paper also shows how the appropriate definition of computer capacity, and in particular Kleinrock's power definition, plays a central role in economies of scale for computer prices.status: publishe

A matrix-geometric solution for the multiserver nonpreemptive priority queueing model with mixed priorities

This paper describes the analysis of multiserver queues with nonpreemptive mixed priorities. Such priority structures occur, for example, in initiator settings within the mainframe operating system MVS: job classes have to be assigned to initiators and their priorities may differ amongst the initiators. Results of the analysis provide insight in how average queue lengths in this priority system behave under different class loads. Bounds have to be defined in order to obtain a matrix-geometric solution and it is shown how this affects the average queue lengths. The results should eventually allow to derive guidelines with respect to initiator definitions.status: publishe

How the Condition Number of the Caudal Characteristic Reflects the Dynamics of a QBD

The spectral radius 'T] of the rate matrix of a QBD is known to be indicative of the tail behaviour of the steady state probability distribution. Therefore 'T] is called the caudal characteristic and is used as a descriptor of the dynamics of the QBD. In this paper, we show that additional information is given by the condition number of the spectral radius, 1\;( 'T]), especially in those cases where 1\;( 'T]) is huge.status: publishe