Tandem Capacity Model (TCM) Manual

• If you are modeling a batch job that runs when the online transaction application is running
at a lower throughput or is shut down, create two models:
◦ One model for the online transaction application during its peak period
◦ One model for the batch job
• If you are modeling a batch job that runs at the same time as the peak period for the online
transaction application, the Measure sample should include all of the batch run and exclude
the online transaction application startup and shutdown.
• Because checking an apportionment method for reasonableness requires several performance
samples, collect at least 4 or 5 samples for each type of transaction. For example, if your
application has 3 transactions (Withdrawal, Deposit, and Update), collect at least 12 to 15
samples.
The samples you collect should be independent of one another. Thus, the samples should have
varying transaction mixes. To get independent samples, you might have to take several
measurements. For instance, to get 12 independent samples, you might have to take 12
one-hour intervals over a 12-hour period. For other applications, you might take measurements
at the same time but over a 12-day period to get 12 independent samples.
In an automated teller machine (ATM) application, for example, you will get different transaction
mixes on a traditional payday (such as the 1st or 16th of the month) versus other days. You
would also get a different transaction mix on a Friday when customers want to withdraw
money for the weekend or on the day before a holiday.
For more information, see the Measure Reference Manual.
Drawing a Process Flow Diagram
The primary function of MeasTCM is to extract and summarize the raw performance data in the
Measure files into process categories for use by TCM in capacity planning. Process categories
represent summarized performance data for any collection of the CPU, PROCESS, DISC, and
DISCOPEN entities that satisfy certain user-specified rules. The rules that define process categories
are contained in the MeasTCM control file.
The concept of process categories is essential to understanding workload apportionment. A process
category is a group of processes whose workload demand values are linked to common processes,
such as a disk process category, a TMF process category, or a server class category. By using
process categories, MeasTCM compresses data by a significant factor. For example, a 14-megabyte
Measure file can be reduced to approximately 2 kilobytes of downloadable data. To understand
how to best create process categories, it is helpful to understand that TCM converts this process
category information to transaction information.
The workload associated with all processes in a category is divided among the transactions.
Categories reduce the number of entities the workload apportionment functions must deal with.
Figure 5 (page 32) shows a simplified picture of the workload apportionment process. In the
workload apportionment process, processes are allocated to transactions.
Drawing a Process Flow Diagram 31