A garbage collection is a technique for automatically collecting memory areas that are used by programs, and allowing other program to use the areas. A JavaVM executes the garbage collection.

Time is required for processing the garbage collection. During execution of a garbage collection, all program processing on JavaVM stop. Therefore, ability to properly execute garbage collection has a great impact on the processing performance of a system.

To avoid resource exclusion for long time by batch applications, the garbage collection control functionality is provided on batch servers. The garbage collection control functionality is the functionality that explicitly executes a full garbage collection, when resource exclusion is not performed. By using the garbage collection control functionality, you can avoid generation of a full garbage collection during the resource exclusion.

The garbage collection control functionality is described below with an example.

If you are not using the garbage collection control functionality, the problems shown in the following figure occur in an environment where the batch processing and online processing are executed in parallel.

Figure 2-13 When you are not using garbage collection control functionality

In this figure, a full garbage collection has occurred during resource exclusion in a batch application. As a result, a batch application processing stops when performing the resource exclusion. During this time, if records under exclusion are referenced from online processing, the online processing also stops until the full garbage collection of batch server ends.

The following figure shows the status, if you use the garbage collection control functionality.

Figure 2-14 If you use garbage collection control functionality

As shown in the figure, when execution request of full garbage is sent, execution of full garbage collection is put on standby, if batch server is performing exclusion of resources.

When a record exclusion is released, a full garbage collection is executed on a batch server. The online processing is also able to access the resources. As a result, you can avoid long time resource exclusion in a batch application.