PL/extJava is a framework for incorporating the application server into the database server and controlling the Java Virtual Machine (Java VM).
Jobs where a client frequently accesses a database using SQL mean a high volume of network traffic between them. As a result, not only these jobs may experience a drop in response, but other job systems may as well. It is possible to reduce network traffic and improve the job processing time by performing business logic, implemented via stored functions, on the database server instead of on the client.
However, if several clients access the database server simultaneously, Java VM multiplexer control and memory resources must be taken into account on the database server if Java VM is run.
PL/extJava can control the Java VM multiplexer control and memory resources using the application server, so stored functions can be executed efficiently even in operation modes that have simultaneous access from many clients.
Figure 7.1 Overview of PL/extJava
Point
In this chapter, PL/extJava stored functions that are registered in the database are referred to as "Java functions". Applications that operate on the Java VM are referred to as "Java applications".
Note
Java functions run on different connections from the ones between the client and the database server. Jobs being migrated to Java functions must therefore be run as independent transactions.
Names of databases that use PL/extJava must be specified in up to 28 bytes. Names of roles for connecting from the application server to the database must be specified in up to 8 bytes.
