Tandem Capacity Model (TCM) Manual

9 The Performance Model
The Performance model is used to answer what-if questions about baseline sample data that has
already been computed in the Workload Apportionment model of TCM. You can analyze estimated
throughputs, host response times, and the number of CPUs and logical disk volumes required to
support different user-defined scenarios. The Performance model also provides presentation-quality
charts for reporting estimated performance results.
This section describes the screens and menus of the Performance model.
Performance Model Components
The Performance model is composed of two submodels that examine apportioned data: the
Consumption model and the Planning Timeline model. These models are represented as two of the
thirteen screens that make up the Performance model. The Performance model consists of the
following main screens:
• Capacity Baseline Actual—a screen that summarizes the source data for the Performance
model. It has the same data as in the WA model, but it is modifiable. This data is used in the
following components of the Performance model:
◦ Consumption model
◦ Planning Timeline model
• Consumption Model—a model used to compute the number of CPUs and disks required to
accommodate one or more performance targets, or vice versa, including:
◦ Target host response time for online transactions
◦ Target CPU utilization, disk utilization, or both for online transactions
◦ Target host response time for batch transactions
◦ Planned OLTP throughputs
◦ Planned batch transactions per task
◦ CPU device type
◦ Disk configuration type (such as audited and nonaudited)
◦ Disk write cache configuration (such as enabled and disabled/NA)
◦ Number of CPUs
◦ Number of logical disk volumes and number of TMF audit trails
• Disk Factors—a screen used to view disk model number, rotational speed (rpm), controller,
disk read seek time and write seek time.
• Planning Timeline—a model used to examine transaction rates and host response times over
six user-specified planning intervals. Several growth scenarios can be specified, including:
◦ Throughput growth
◦ Number of CPUs, disks, or both over time
◦ CPU type
◦ Disk configuration type
136 The Performance Model