scholarly journals ANALISIS PERFORMANSI SERVER SISTEM INFORMASI AKADEMIK UNIVERSITAS MERCU BUANA DENGAN OPEN QUEUEING NETWORK

2015 ◽  
Vol 7 (2) ◽  
pp. 244
Author(s):  
Desi Ramayanti
Keyword(s):  
Service Time ◽  
Queueing Network ◽  
Arrival Rate ◽  
Service Demand ◽  
Open Queueing Network ◽  
Data Error ◽  
Resource Service ◽  
Time Resource

SIA (Sistem Informasi Akademik) merupakan sebuah sistem informasi penting yang berkaitan dengan nilai yang sudah diperoleh untuk setiap matakuliah yang telah diambil, status dari mahasiswa pada semester terkait, dll. SIA ini akan selalu diakses oleh mahasiswa dan juga dosen di lingkungan UMB, baik pada setiap awal semester, pertengahan semester atau pada akhir semester. SIA merupakan fitur  penting yang harus tetap available setiap saat, dan mampu melayani ribuan user dengan baik. Keterlambatan data (delay), kehilangan data (lost) dan kerusakan data (error), harus menjadi point penting dalam sebuah system, karena jika ketiga hal tersebut terjadi, maka nilai informasi akan berkurang atau menjadi tidak berarti lagi, dan hal ini akan sangat merugikan, khususnya kepada mahasiswa sebagai konsumen yang wajib mendapatkan pelayanan terbaik. Maka dikarenakan hal tersebut, maka penulis melakukan penelitian berkaitan dengan performansi SIA saat ini. Dalam penelitian ini, penulis melakukan analisis performansi SIA yang terkait dengan arrival rate resource, service time resource utilisasi resource, Rata-rata jumlah kunjungan ke resource, service demand resourcedan arrival rate maksimum dari server. Dari hasil analisis maka diperoleh kesimpulan bahwa performansi dari server SIA yang ada saat ini kurang maksimum dengan jumlah mahasiswa yang ada. Server Sistem Informasi Akademik saat ini hanya mampu melayani request per detik sebanyak 7.278 request. Sedangkan arrival rate yang ada yaitu 8.88 request per detik, sehingga kemungkinan lost request adalah 21.98%.

scholarly journals Modeling and performance analysis of shuttle-based compact storage systems under parallel processing policy

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259773
Author(s):  
Lei Deng ◽  
Lei Chen ◽  
Jingjie Zhao ◽  
Ruimei Wang
Keyword(s):  
Parallel Processing ◽  
Storage Systems ◽  
Current System ◽  
Queueing Network ◽  
Arrival Rate ◽  
Width Ratio ◽  
Storage And Retrieval ◽  
Sequential Processing ◽  
Open Queueing Network ◽  
And Performance

Short response time for order processing is important for modern warehouses, which can be potentially achieved by adopting appropriate processing policy. The parallel processing policy have advantages in improving performance of many autonomous storage and retrieval systems. However, researchers tend to assume a sequential processing policy managing the movement of independent resources in shuttle-based compact storage systems. This paper models and analyses a single-tier of specialized shuttle-based compact storage systems under parallel processing policy. The system is modeled as a semi-open queueing network with class switching and the parallel movement of shuttles and the transfer car is modeled using a fork-join queueing network. The analytical model is validated against simulations and the results show our model can accurately estimate the system performance. Numerical experiments and a real case are carried out to compare the performance of parallel and sequential processing policies. The results suggest a critical transaction arrival rate and depth/width ratio, below which the sequential processing policy outperforms the parallel processing policy. However, the advantage of sequential processing policy is decreasing with the increasing of shuttle number, transaction arrival rate and depth/width ratio. The results also suggest an optimal depth/width ratio with a value of 1.75 for minimizing the expected throughput time in the real system. Given the current system configurations, the parallel processing policy should be considered when the number of shuttles is larger than 2 or the transaction arrival rate is larger than 24 per hour.

scholarly journals Analysis of semi-open queueing networks using lost customers approximation with an application to robotic mobile fulfilment systems

OR Spectrum ◽  
2021 ◽  
Author(s):  
Sonja Otten ◽  
Ruslan Krenzler ◽  
Lin Xie ◽  
Hans Daduna ◽  
Karsten Kruse
Keyword(s):  
Queueing Networks ◽  
Queueing Network ◽  
Arrival Rate ◽  
Second Step ◽  
Original Network ◽  
Theoretical Methods ◽  
Solution Approach ◽  
Open Queueing Networks ◽  
Open Queueing Network ◽  
Storage Area

AbstractWe consider a semi-open queueing network (SOQN), where one resource from a resource pool is needed to serve a customer. If on arrival of a customer some resource is available, the resource is forwarded to an inner network to complete the customer’s order. If no resource is available, the new customer waits in an external queue until one becomes available (“backordering”). When a resource exits the inner network, it is returned to the resource pool. We develop a new solution approach. In a first step we modify the system such that new arrivals are lost if the resource pool is empty (“lost customers”). We adjust the arrival rate of the modified system such that the throughputs in all nodes of the inner network are pairwise identical to those in the original network. Using queueing theoretical methods, in a second step we reduce this inner network to a two-station system including the resource pool. For this two-station systems, we invert the first step and obtain a standard SOQN which can be solved analytically. We apply our results to storage and delivering systems with robotic mobile fulfilment systems (RMFSs). Instead of sending pickers to the storage area to search for the ordered items and pick them, robots carry shelves with ordered items from the storage area to picking stations. We model the RMFS as an SOQN to determine the minimal number of robots.

Stationary Poisson departure processes from non-stationary queues

1986 ◽  
Vol 23 (1) ◽  
pp. 256-260 ◽  
Author(s):  
Robert D. Foley
Keyword(s):  
Poisson Process ◽  
Service Time ◽  
Queueing Systems ◽  
Arrival Rate ◽  
Distribution Functions ◽  
Arrival Process ◽  
Service Time Distribution ◽  
Departure Process ◽  
Infinite Server ◽  
Departure Processes

We present some non-stationary infinite-server queueing systems with stationary Poisson departure processes. In Foley (1982), it was shown that the departure process from the Mt/Gt/∞ queue was a Poisson process, possibly non-stationary. The Mt/Gt/∞ queue is an infinite-server queue with a stationary or non-stationary Poisson arrival process and a general server in which the service time of a customer may depend upon the customer's arrival time. Mirasol (1963) pointed out that the departure process from the M/G/∞ queue is a stationary Poisson process. The question arose whether there are any other Mt/Gt/∞ queueing systems with stationary Poisson departure processes. For example, if the arrival rate is periodic, is it possible to select the service-time distribution functions to fluctuate in order to compensate for the fluctuations of the arrival rate? In this situation and in more general situations, it is possible to select the server such that the system yields a stationary Poisson departure process.

Hitting time in an M/G/1 queue

1999 ◽  
Vol 36 (03) ◽  
pp. 934-940 ◽  
Author(s):  
Sheldon M. Ross ◽  
Sridhar Seshadri
Keyword(s):  
Service Time ◽  
Time Distribution ◽  
Arrival Rate ◽  
Hitting Time ◽  
Service Time Distribution ◽  
Expected Time ◽  
Efficient Simulation ◽  
Simulation Procedure ◽  
Poisson Arrival ◽  
Stationary Delay

We study the expected time for the work in an M/G/1 system to exceed the level x, given that it started out initially empty, and show that it can be expressed solely in terms of the Poisson arrival rate, the service time distribution and the stationary delay distribution of the M/G/1 system. We use this result to construct an efficient simulation procedure.

scholarly journals Performance measurement and analytic modeling of a web application

2021 ◽  
Author(s):  
Yasir Shoaib
Keyword(s):  
Web Application ◽  
Web Applications ◽  
Research Work ◽  
Queueing Network ◽  
Performance Model ◽  
Load Testing ◽  
Performance Models ◽  
Analytic Modeling ◽  
Service Demand ◽  
Time Required

The performance characteristics such as throughput, resource utilization and response time of a system can be determined through measurement, simulation modeling and analytic modeling. In this thesis, measurement and analytic modeling approaches are applied to study the performance of a Apache-PHP-PostgreSQL web application. Layered Queueing Network (LQN) analytic modeling has been used to represent the system's performance model. The measurements found from load testing are compared with model analysis results for model validation. This thesis aims to show that LQN performance models are versatile enough to allow development of highly granular and easily modifiable models of PHP-based web applications and furthermore are capable of performance prediction with sufficiently high accuracy. Lastly, the thesis also describes utilities and methods used for load testing and determination of service demand parameters in our research work which would aid in shortening time required in development and study of performance models of similar systems.

Stability condition for a single-server retrial queue

1993 ◽  
Vol 25 (03) ◽  
pp. 690-701 ◽  
Author(s):  
Huei-Mei Liang ◽  
V. G. Kulkarni
Keyword(s):  
Stability Condition ◽  
Service Time ◽  
Retrial Queue ◽  
Arrival Rate ◽  
Retrial Queues ◽  
Single Server ◽  
Sufficient Stability Condition ◽  
Sufficient Stability ◽  
The Mean ◽  
The Stability

A single-server retrial queue consists of a primary queue, an orbit and a single server. Assume the primary queue capacity is 1 and the orbit capacity is infinite. Customers can arrive at the primary queue either from outside the system or from the orbit. If the server is busy, the arriving customer joins the orbit and conducts a retrial later. Otherwise, he receives service and leaves the system. We investigate the stability condition for a single-server retrial queue. Let λ be the arrival rate and 1/μ be the mean service time. It has been proved that λ / μ < 1 is a sufficient stability condition for the M/G /1/1 retrial queue with exponential retrial times. We give a counterexample to show that this stability condition is not valid for general single-server retrial queues. Next we show that λ /μ < 1 is a sufficient stability condition for the stability of a single-server retrial queue when the interarrival times and retrial times are finite mixtures of Erlangs.

scholarly journals Diffusion-Scale Tightness of Invariant Distributions of a Large-Scale Flexible Service System

2015 ◽  
Vol 47 (01) ◽  
pp. 251-269 ◽  
Author(s):  
A. L. Stolyar
Keyword(s):  
Diffusion Process ◽  
Service Time ◽  
Large Scale ◽  
Service System ◽  
Arrival Rate ◽  
Asymptotic Regime ◽  
Invariant Distributions ◽  
Multiple Customer Classes ◽  
The Mean ◽  
Diffusion Scale

A large-scale service system with multiple customer classes and multiple server pools is considered, with the mean service time depending both on the customer class and server pool. The allowed activities (routeing choices) form a tree (in the graph with vertices being both customer classes and server pools). We study the behavior of the system under a leaf activity priority (LAP) policy, introduced by Stolyar and Yudovina (2012). An asymptotic regime is considered, where the arrival rate of customers and number of servers in each pool tend to ∞ in proportion to a scaling parameter r, while the overall system load remains strictly subcritical. We prove tightness of diffusion-scaled (centered at the equilibrium point and scaled down by r −1/2) invariant distributions. As a consequence, we obtain a limit interchange result: the limit of diffusion-scaled invariant distributions is equal to the invariant distribution of the limiting diffusion process.

scholarly journals Diffusion-Scale Tightness of Invariant Distributions of a Large-Scale Flexible Service System

2015 ◽  
Vol 47 (1) ◽  
pp. 251-269 ◽  
Author(s):  
A. L. Stolyar
Keyword(s):  
Diffusion Process ◽  
Service Time ◽  
Large Scale ◽  
Service System ◽  
Arrival Rate ◽  
Asymptotic Regime ◽  
Invariant Distributions ◽  
Multiple Customer Classes ◽  
The Mean ◽  
Diffusion Scale

A large-scale service system with multiple customer classes and multiple server pools is considered, with the mean service time depending both on the customer class and server pool. The allowed activities (routeing choices) form a tree (in the graph with vertices being both customer classes and server pools). We study the behavior of the system under a leaf activity priority (LAP) policy, introduced by Stolyar and Yudovina (2012). An asymptotic regime is considered, where the arrival rate of customers and number of servers in each pool tend to ∞ in proportion to a scaling parameter r, while the overall system load remains strictly subcritical. We prove tightness of diffusion-scaled (centered at the equilibrium point and scaled down by r−1/2) invariant distributions. As a consequence, we obtain a limit interchange result: the limit of diffusion-scaled invariant distributions is equal to the invariant distribution of the limiting diffusion process.

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