Tandem Capacity Model (TCM) Manual

numbers in a given row. The numbers can be decimal fractions, such as 0.5. The numbers in one
row have no effect on any of the other rows. The best way to read the table is across.
In the following table, the CPU and disk consumption cost of the linehandler category is spread
equally (on a per-transaction basis) between Withdrawal and Deposit. Deposit Server is charged
entirely to Deposit. TCP is charged to Withdrawal and Deposit with relative weights of 2 and 1,
respectively. TCP must do twice as much work for a Withdrawal transaction as for a Deposit
transaction.
DepositWithdrawal
11Line handler
10Deposit Server
12TCP
The following guidelines apply to disk and TMF process categories:
• All transaction values for the single disk process category (type D category) in the
Apportionment Weights table should be 1.
• All transaction values for the single TMF process category (type T category) should be 1 for
audited transactions or 0 for nonaudited transactions.
If all transaction values for any category are 0, an error message appears because the process
category CPU and disk seconds must be allocated to a transaction.
TCM Expert
You can use the TCM Expert feature to create the Apportionment Weights table automatically. For
more information, see “Generating Expert Apportionment Weights” (page 182).
Example of a Transaction Count Table
The starting point for transaction count analysis is the process flow diagram. Arrows indicate a
transaction’s path through the process categories. Each transaction has its own set of arrows.
Figure 14 (page 72) shows a sample process flow diagram.
Figure 14 Process Flow Diagram
The Transaction Count table for this example calculates the transaction counts for Deposit and
Withdrawal:
• Rows correspond to process categories.
• Below each transaction are Rcv and Send columns.
• Table entries are coefficients (multipliers) for category Rcv/Send counts.
72 Creating a WA Model