To illustrate it, we will refer to our DataSource example. In the first chapter, we configured a pool and a data source. The data source was just a name in the JNDI that the application was using to find the data source and later uses it in its JPA layer. This is pretty much what a data source is: a connection factory. What is crucial here is the way the connections are managed.
Most of the time, the production data sources are remote processes or, at least, require a network connection. If you remember our MySQL connection URL, we used the following:
This is a very common development configuration and it connects to localhost. Thus, the network cost is the machine local loop cost, which ...