• Improved throughput and resource utilization. A transaction consists of
many steps. Some involve I/O activity; others involve CPU activity. The CPU
and the disks in a computer system can operate in parallel. Therefore, I/O
activity can be done in parallel with processing at the CPU. The parallelism
of the CPU and the I/O system can therefore be exploited to run multiple
transactions in parallel. While a read or write on behalf of one transaction
is in progress on one disk, another transaction can be running in the CPU,
while another disk may be executing a read or write on behalf of a third
transaction. All of this increases the throughput of the system—that is, the
number of transactions executed in a given amount of time. Correspondingly,
the processor and disk utilization also increase; in other words, the processor
and disk spend less time idle, or not performing any useful work.