1. Working with Oracle Forms
  2. Integration
  3. Configuring and Managing Java Virtual Machines
  4. Design-time Considerations

Design-time Considerations

This section describes some of the design-time considerations.

The following sections are included:

Re-importing Your Java Code

If you used the Java Importer feature of Oracle Forms prior to the availability of JVM Pooling, you will need to reimport your Java classes before using JVM pooling. When you originally imported your Java classes, PL/SQL wrappers for the Java classes were generated, which you can see in the Program Units that were created in your Form. However, the PL/SQL wrappers that are generated by the Java Importer to utilize JVM pooling are different.

From Oracle Forms Services 10g and later, the Java Importer generates the new PL/SQL wrappers. If you want to use the Java Importer, but do not wish to take advantage of JVM pooling, the in-process JVM will work with the new PL/SQL wrappers. It will also continue to work with the older-style PL/SQL wrappers.

About Sharing Static Variables Across Multiple JVMs

One advantage of JVM pooling is the ability to share data between instances of a class by using static variables. However, static variables will be shared between instances of the same class within a JVM, but not across JVMs. You will need to plan accordingly.

For example, suppose your loan class has a static variable called interestRate because all instances use the same interest rate in calculations. If you are using only one JVM, and one of the instances of your loan class changes interestRate, all of the other instances will be affected (which is what you want).

However, if the JVM controller has one or more child JVMs, there may be at least two JVMs. If interestRate changes in one JVM, the loan instances in the other JVMs won't see this new value, see Child JVM Processes. Prior to JVM pooling, if you changed interestRate it would not affect any other instances because each Oracle Forms Runtime process had its own in-process JVM.

If you rely on static variables to share information between instances of your class, ensure that no child JVM is spawned by setting maxsessions to 65535.