Fig. 11.1.4 The elements of response time.At step (1), a transaction is initiated. A customer wants to see how much is in his/her
account. A shelf stocker wants to place an item on the shelf of a store. A clerk wants to
mark the successful manufacture of an order. An airline wants to upgrade a customer.
These are all forms of initiating a transaction.
At step (2), the transaction arrives at the computer. The program goes into execution.
Variables are initialized. Calculations are made. Algorithms are executed. Then,
somewhere along the line of doing its processing, the computer program discovers that it
needs to go to a database and find some data in order to execute.
At step (3), a request is made to the DBMS in order to find data. The DBMS honors the
request and goes off to search for some data. Upon finding the data, the DBMS packages
the data and sends it back to the computer.
The program commences processing again. The program discovers that it needs more
data so the program issues another request for data to the DBMS. Data are returned to
the program.
Finally, upon conclusion of the program—at step (4)—the program inside the computer is
Chapter 11.1: Operational Analytics: Response Time