How to determine if OACore JVM Sizing is Appropriate or Not

cd $LOG_HOME/ora/10.1.3/opmn/
ls -ltr default_group~oacore*

grep 'Full GC' default_group~oacore* | wc -l
grep 'Unloading class' default_group~oacore* | grep 'Full GC' | wc -l

If you see there are multiple cases when Full GC is happening then, it is understood that JVM sizing in not proper.

Take following actions for this:
1. Increase the Number of OACore JVMs
2. Increase the JVM Heap Size
3. Make sure you are not using many parallel thread for GC.