Java Programming with Oracle SQLJ

8.3. Multithreaded SQLJ Programs

A Java program can perform a number of actions in parallel, with each action being performed by a separate process. Such a process is also known as a thread. For example, a multithreaded program might perform database access using one thread while another thread handles the display. In the case of a SQLJ program, you might want to perform several SQL operations in parallel using a separate thread for each one. Multithreading is a very powerful feature of the Java language. The downside to writing a multithreaded program is the additional complexity of dealing with the thread model.

If a SQLJ program were to use multiple threads, then the program would run faster, right? Not always: it depends on where the program runs. If the program is deployed in the Oracle JServer JVM (described in Chapter 6), then the multithreaded program may not run faster than a comparable program that is not multithreaded. This is because the JServer JVM executes each thread serially through a single operating system thread and schedules the execution of each thread using a round-robin algorithm. However, this doesn't mean that the JServer JVM is slow! The JServer JVM has other ways to increase the performance of Java programs. If a SQLJ program is not going to be run using the JServer JVM, then the program may benefit from the use of threads.

8.3.1. Designing a Multithreaded SQLJ Program

How would you structure a SQLJ program to use threads? The basic problem that must ...