Tandem Capacity Model (TCM) Manual

Checking an Apportionment Method
Once an apportionment method has been created by modifying either the default apportionment
tables of a new model or the apportionment tables of an existing model, and the apportionment
formulas have been generated, you need to analyze the results to determine the reasonableness
of the method.
In general, an Apportionment Weights table can be viewed as reasonable if CPU and disk demands
per transaction are relatively constant across many performance samples with varying transaction
mixes and throughput levels. The requirement for a variety of transaction mixes is crucial. If mixes
do not vary, any apportionment method will appear to be reasonable but might not be.
To make sure a method is reasonable, first save a model for each apportionment method and
follow the steps in “Updating History With Several Examples” (page 82).
Because checking an appropriate apportionment method requires several performance samples,
the following procedure is based on the assumption that you have already collected these samples
on the NonStop host system using Measure and processed them using MeasTCM. The number of
samples should be at least 4 to 5 times the number of defined transactions. For example, if your
application has 3 transactions named Withdrawal, Deposit, and Customer Update, collect at least
12 to 15 samples. The samples should have different transaction mixes and be at varying utilizations.
Updating History With Several Examples
Creating additional WA models involves loading additional performance data samples into your
WA model for apportioning. This process allows you to apportion a variety of data samples to
determine the reasonableness of the apportionment method. Creating additional models allows
you to update the Capacity History database with many samples, to select appropriate samples
for modeling, and to create baseline data for input to the Performance model.
The following procedure results in one or more saved, apportioned WA models with an updated
history:
1. To download performance data samples to the PC, follow the download procedure you
normally use in Windows. All CSV files for the same application or set of applications should
be kept in the same folder, and all CSV files must have the extension .CSV. TCM detects any
truncated data and issues an error message.
2. If you are already in the WA model, load a CSV file into the current model. (See page “Loading
a CSV Sample Into a WA Model” (page 240).)
If you are at the “TCM Initial Menu” (page 66):
1. Select Work With Existing Model. The Open WA Model dialog box displays the available
WA models.
2. Log on as an administrator or super user. For more information about this step, see “Changing
Authorization Levels” (page 69).
3. From the Models field, select an existing apportioned model to use as a template for all the
new WA models that you want to create.
4. Click Update History and Display List of CSV Files. Then click Open.
The Create New WA Model dialog box appears.
5. Select the CSV file or files to load and click OK.
When you are finished, each data sample will have a corresponding sample WA model in
the folder.
To update history with several examples:
1. Select TCM Expert from the “TCM Initial Menu” (page 66).
The Specify Custom Directory dialog box appears.
2. Select a custom folder and click OK.
82 Creating a WA Model