There is another way of thinking of the speeds that can be attained. That way is the
vehicle you are in is as slow as the vehicle in front of you. And if the vehicle in front of
you is a large, slow vehicle, then that is your optimal speed.

Stated differently, how fast can a Porsche run on a race track? The Porsche can run as
fast as the slowest car in front of the Porsche.

The way then to achieve speed and efficiency in the online transaction environment is to
allow only small fast-moving transactions into the system.

The size of an online transaction is measured in terms of how much data the transaction
accesses and whether the transaction does update. The update a transaction does affects
the amount of records that are locked during the update process. In general, an online
DBMS “locks” records that might be updated while a transaction is in execution.

Fig. 7.2.7 shows what constitutes a “large” online transaction and a “small” online
transaction.

Fig. 7.2.7 A small transaction and a large transaction.

The Standard Work Unit

The standard work unit then states “in order to achieve good and consistent online
transaction time, each online transaction running in the system needs to be small and

Chapter 7.2: The Standard Work Unit