Tandem Capacity Model (TCM) Manual

With the Performance model, you can explore possibilities by imposing constraints on the
modeling process. You can impose constraints on either hardware configuration or performance
factors. For instance, you can ask what will happen to response time if the average transaction
rate doubles but the hardware configuration remains the same. Or you can ask what is the
lowest-cost combination of CPUs and disk drives that will maintain an average response time
below two seconds.
The Performance model generates presentation-quality charts of forecasted throughputs and
host response times.
Figure 1 TCM Architecture
TCM User Levels
TCM is designed for users who are familiar with capacity planning methodology and techniques:
• Capacity planners
Capacity planners have a good understanding of capacity planning in general, but they might
not thoroughly understand its application to HP NonStop systems. Planners define and analyze
alternative capacity management approaches and have access to the basic TCM commands
necessary to perform these tasks.
They establish explicit performance objectives for each category of work and periodically
make predictions of how various workloads will grow. Capacity planners assess upgrade
alternatives and recommend the best upgrade alternative.
• TCM administrators
TCM administrators have knowledge of capacity planning on HP NonStop systems as well as
a thorough understanding of the application under study. TCM administrators define and
20 Introduction