Learning JPA is a road marked with a lot of questions. Some of the notorious questions include: "What is actually a persistence-unit?," "What is an extended persistence-context?," "Why is wrong to fetch read-only data as entities?," "Why should I care aboutRESOURCE_LOCALorJTA?," and so on and forth.
This article targets people that are confused by the JPA transaction types,RESOURCE_LOCAL, andJTA. But, let's take it step by step.