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A Practical Approach to Capacity Modelling

Links to Modeling Tools

Here are the links I have found to modeling tools, both simulation and analytic, and modeling information. Some I have used, some I have read about and others look interesting but I haven't any first hand information about them. The comments are strickly my opinions and are focused on how useful I think the tools are for modeling computer systems and applications. My main interest when looking at each tool is it's usefulness for The Simalytic Modeling Technique. Please look at each tool in view of your own situation and requirements. Many of these companies have very good academic and research programs. All information presented here was accurate to the best of my knowledge at the time I collected it, but I make NO guarantees! Comments are welcome, just email


Books on Modeling

The Practical Performance Analyst: Performance-By-Design Techniques for Distributed Systems (McGraw-Hill Series on Computer Communications) by Neil J. Gunther. 1998. McGraw Hill Text; ISBN: 0079129463

Capacity Planning and Performance Modeling; From Mainframes to Client-Server Systems by Daniel A. Menasce, Larry W. Dowdy, Virgilio A. F. Almeida, Lawrence W. Dowdy. 1994. Prentice Hall; ISBN: 0130354945

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General Purpose Modeling Tools

Dr. Norton has had some experience with these tools but the descriptions here should NOT be viewed as recommendations, only as his opinion.


Developed for the manufacturing industry but very usable for other types of models, such as computer systems. Supports connections to Visual Basic and Excel (really any DDE application) and does nice on-screen animation.

Simul8 Corporation (formerly Visual Thinking International Ltd)


Developed for the manufacturing industry. Might be usable for computer systems, but the demo I used would not allow models to be saved (check for yourself to see if that is still the case), so I did not do much with it.

PROMODEL Corporation


A library of C routines for use in constructing process-oriented, discrete-event simulation models (requires developing a simulation program using the libraries).

Mesquite Software


Tools developed for SPE (Software Performance Engineering); understanding performance during software design. Does both analytic (MVA) and simulation (CSIM) for different views of an application. Very useful for modeling the early stages of software designs to insure the application will meet the required performance goals. User interface was originally developed on the Mac and the early version was awkward for Windows users, I have not used the latest version. Also, Dr. Connie Smith, the designer of SPE*ED, has published several extremely good books and many papers that should be required reading for all application developers.

Performance Engineering Services


Developed for the manufacturing industry, but looks interesting for computer systems and applications. I have not had a chance to look at it in depth. Comments welcome.

Imagine That, Inc.

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Platform Specific Modeling Tools

PRO-SIM and Athene

Pro-Sim was a simulation tool (does not seem to be currently available) and Athene is a platform-centric tool. I have had limited experience with these tools (and it was some time ago).


Best/1 for MVS/Unix/VM/VMS/NT

Very robust platform-centric analytic tools that include data collection for each of the platforms. The Best/1 tools go beyond modeling to provide performance analysis and capacity planning, but they are focused on existing workloads and do not have very good support for modeling application not yet running.

These products were developed at BGS Systems by Jeff Buzen, Robert Goldberg, and Annie Shum and were offered by BMC after the merger. However, it seems that they are not currently offered but they are still worth looking at because they represent the best Platform Specific Modeling Tools I have ever seen. Look at the authors' 1978 seminal paper: BEST/1 - Design of a tool for computer system capacity planning.

BMC (was BGS Systems)

Business Process Specific Modeling Tools

STELLA and ithink-is

The major difference is documentation. ithink audience: business (BPR, Strategic Planning, Financial Analysis). STELLA II audience: educational and research (natural and social sciences).

isee Systems, Inc.

Vensim PLE

Very similar to STELLA. Free for academic use, cheap for commercial purposes (90 day trial of full tool, if still available).

Ventana Systems, Inc.

Powersim Constructor 2.5

Like Stella and Vensim but a much better user interface. Downloadable demo (full function but limits size of models, if still available). This tool was used in Dr. Norton's paper Don’t Predict Applications When You Should Model the Business.


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IASTED - Home Page

CMG - Computer Measurement Group



ACM Transactions on Modeling and Computer Simulation (TOMACS)

Society For Computer Simulation International

Winter Simulation Conference

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