Tandem Capacity Model (TCM) Manual

name, TCM updates this name in the custom folder field of the dialog box and also makes
this the location of your working session.
3. Click OK to close the dialog box.
4. Select TCM Expert > Pick Best CSV Sample.
The Pick Best CSV Sample dialog box appears.
5. Select the Capacity History file from which to pick the CSV sample and click OK.
TCM Expert picks the best CSV sample.
6. If you want to load this CSV sample into the Performance model, click Create.
TCM loads the CSV sample into the Performance model and displays the Capacity Baseline
Plan for the CSV sample. You are now in the Performance model and have left TCM Expert.
Viewing or Changing Expert Parameters
To view the global parameters for TCM Expert, select TCM Expert > TCM Expert Parameters.
To change the global parameters for TCM Expert:
1. Select TCM Expert from the “TCM Initial Menu” (page 66).
The Specify Custom Directory dialog box appears.
2. Specify a custom folder and click OK.
3. Select TCM Expert > TCM Expert Parameters.
The TCM Expert Parameters dialog box appears.
4. Accept the default Capacity History time period (six months) or specify a new one.
This field specifies the time range that is used in three situations:
• The time range that is checked for transaction cost consistency when you select Generate
Expert.
• The time range that is checked for transaction cost consistency when you select Update
History with Selected CSV Samples.
• The time range that is used when you select Pick Best Sample.
The default time period is six months.
5. If you are logged on as an administrator (with the access level of system administrator or
higher), accept the default Cache Miss Factor or specify a new one.
The Cache Miss Factor specifies the relative CPU cost to the disk process of a cache miss as
compared with a cache hit. The default settings assume that it takes twice as much CPU time
to get data off the disk than to get data from cache (memory). That is, a cache miss costs twice
as much as a cache hit. A TCM administrator or superuser can modify this factor.
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, and 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.
Viewing or Changing Expert Parameters 187