What app/VM is throwing the OutOfMemoryException: the WebLogic JVM or your app JVM? You first need to inspect the memory requierements of your application throwing the OutOfMemoryException. Perhaps you really need more memroy, so you need to increase memory with -Xmx parameter of Java.
Of course, your application can also have a memory leak, meaning than you still hold object references even when you don't need them anymore. Use jConsole to inspect the running application. JConsole is a monitor tool included in the Java SDK.