Tandem Capacity Model (TCM) Manual

6. Accept the default CPU Pathlength Threshold or specify a new one.
The CPU Pathlength Threshold field specifies the point at which a query transaction is considered
either an OLTP or batch transaction. The default setting is two seconds. Small demand queries
taking less than two seconds are considered OLTP transactions, large demand queries taking
longer than two seconds are considered batch transactions. Any TCM user can modify this
factor.
7. Click OK. TCM Expert uses the new parameters.
For more information, see Chapter 10: “Using TCM Expert”.
Changing Individual Priorities
To change specific individual process category priorities, use the Workload Detail by Category
screen in the WA model.
To change individual priorities:
1. Open a WA model.
2. Make sure you are logged on as an administrator or super user.
3. Select Find > Workload Detail by Category.
4. Select Options > Unprotect Admin Fields.
5. Enter the customized priorities in the Priority column for the process categories that you want
to change.
6. Select Options > Protect Admin Fields.
7. Select Options > Calculate Now (F12).
8. To save the model, by select Save or Save As from the File tab.
For more information, see “Workload Detail by Category Screen” (page 121).
Changing Passwords
If multiple users will be working with TCM, change the default passwords to maintain system
security.
To change passwords:
1. Log on as an administrator or super user.
2. Open a WA model or a Performance model.
3. Select Options > Change Password. The Change TCM Password dialog box appears.
4. Enter your old password (or the default password) in the Old Password field.
5. Enter the new password you want to use in the New Password field.
6. Click OK. A message confirms the change.
For more information, see “Security” (page 68).
Checking an Apportionment Method
Once an apportionment method has been created (see modifying the default apportionment tables
of a new model or the apportionment tables of an existing model,) and the apportionment formulas
have been generated (see generating apportionment formulas), you need to analyze the results to
determine the reasonableness of the method.
To ensure the accuracy of the TCM modeling results, examine the reasonableness of both the
performance data sample and the method used to apportion this data. Selecting an appropriate
method involves collecting and apportioning multiple performance samples and then analyzing
the results.
Because checking an apportionment method requires several performance samples, 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, you should
collect at least 12 to 15 samples. The samples should have different transaction mixes and be at
varying utilizations.
234 Common TCM Procedures