Tandem Capacity Model (TCM) Manual

5. # Disks, Disk Model, and Config—Directly Modifiable
#Disks, Disk Model and Config are the desired number, Model, configuration of disks for any
of the Scenario dates in the Planning Timeline model. Valid disk model numbers are listed in
the Disk Factors screen. Valid disk configuration types are listed in the scratch areas of the
TCM Parameters screen. Initially, the first column values match the actual number and model
of disks, as shown in the first date column in the series. Columns 2 through 8 initially match
the Actual data, or the Plan data from the Consumption Model depending on the value of the
First Plan Scenario From Consumption Model button. When you type over any value, the new
value automatically propagates to the fields on the right. If you enter a disk model number
that is not listed in the Disk Conversion Factor screen, a red "?Bad Disk Model" value appears
in the row between the top and bottom sections of the screen when you press Calculate Now
(F9).
NOTE: TCM does not model disk space.
6. Disk Write Cache—Directly Modifiable
Disk Write Cache is the desired write cache configuration for any of the Scenario dates in
the Planning Timeline model. Valid Write Cache configurations are listed in the scratch areas
of the TCM Parameters screen. Initially, the first column values match the actual configuration
as shown in the first date column in the series. Columns 2 through 8 initially match the Actual
data, or the Plan data from the Consumption Model depending on the value of the First Plan
Scenario From Consumption Model button. When you type over any value, the new value
automatically propagates to the fields on the right.
7. TMF audit trails—Directly Modifiable
TMF Audit Trails is the desired number of TMF audit trails for any of the Scenario dates in the
Planning Timeline model. For audit disk configurations, TMF trails can be between 1 and 16.
For unaudited configurations it is NA (not applicable). Initially, the first column values match
the actual configuration as shown in the first date column in the series. Columns 2 through 8
initially match the Actual data, or the Plan data from the Consumption Model depending on
the value of the First Plan Scenario From Consumption Model button. When you type over
any value, the new value automatically propagates to the fields on the right.
8. Total Online TPS—Not Directly Modifiable
Total TPS, TPH, TPD, or TPM is the planned throughput for each transaction in userspecified
planning units (transactions per second, hour, day, or month) for each time period.
9. Avg Online Resp Time—Not Directly Modifiable
Avg Online Resp Time is the estimated host response time for each transaction, given its
throughput and excluding communications line time, for each time period.
10. Avg Batch Resp Time—Not Directly Modifiable
Avg Batch Resp Time is the estimated host response time for each transaction, given its
throughput and excluding communications line time, for each time period. This result is based
on the multiple Priority Closed Queueing model. For more information, see Chapter 7:
“Modeling Batch Workloads”, and Appendix D: “TCM Response Time Formulas”.
11. TPS (TPM or TPH)—Directly Modifiable
TPS, TPM or TPH is the throughput for each transaction for each time period. To predict host
response times and utilizations for a specific transaction for a specific date, simply type over
the value in the appropriate field. Type zero (0) in the field if you do not want to include that
transaction in the model’s projections. Throughput amounts to the right of the modified field
automatically increment according to the specified rate.
146 The Performance Model