JVM pooling is a feature that works in conjunction with the Java Importer. The Java Importer allows developers at design-time to reference Java classes from PL/SQL within the Forms Builder. At runtime, Forms uses a JVM (Java Virtual Machine) to execute the Java code. This expands the capabilities of a Forms application because it can now do operations that can't be done natively in Forms. For more information the Java Importer topics in the Oracle Forms Developer Online Help.
JVM pooling allows administrators to consolidate the number of JVMs used, so that the Forms sessions can share JVMs, rather than each one having it's own copy. This can result in a large reduction of memory consumption, thus freeing up more resources on your server.
For more information on JVM Pooling, see Oracle Application Server 10g Forms Services Deployment Guide.