Tandem Capacity Model (TCM) Manual

Modifying Percentile Response Times
TCM can provide the following results for OLTP transactions: average, 90th, 95th, or 99th percentile.
The default is average. If you change from the default (average) to percentile response times, TCM
uses percentile response time for OLTP transactions in all screens of the Performance model.
For example, if the response time is 1 second and average response time is selected, the average
response time of transactions is 1 second. If 90th percentile is selected, 90 percent of the transactions
have a response time of less than or equal to 1 second.
To change to a different response time method:
1. Open a Performance model.
2. Select Options > Select Response Time Method. The Select Response Time Method dialog box
appears.
3. Select the response time method you want (Average is the default) and click OK.
4. A confirmation dialog appears. Click OK to dismiss it.
Using the Consumption Model
The TCM Consumption model is used primarily to predict the number of CPUs and logical disk
volumes required for a given scenario. The capacity planner can specify any of the following
parameters:
• Target online CPU or disk utilization or both expressed in average percentages
• Target online host response time in seconds (either average or percentile)
• Target batch response time
• Planned online throughputs in transactions per second, minute, hour, day, or month
• Planned CPU and disk type
• Number of CPUs, logical disk volumes or both
• Planned number of transactions per task for batch transactions
To use the Consumption model:
1. Open a Performance model.
2. Select Consumption model. The Consumption model appears. Figure 24 (page 90) shows a
sample Consumption model screen.
Figure 24 Consumption Model Screen
90 Creating a Performance Model