OutofMemory error

First application(program) level...

What is Heap space in Java?

When a Java program started Java Virtual Machine gets some memory from Operating System. Java Virtual Machine or JVM uses this memory for all its need and part of this memory is call java heap memory. Heap in Java generally located at bottom of address space and move upwards. whenever we create object using new operator or by any another means object is allocated memory from Heap and When object dies, memory goes back to Heap space in Java

(We can increase or change size of Java Heap space by using JVM command line option -Xms, -Xmx and –Xmn)

Java Heap and Garbage Collection

As we know objects are created inside heap memory and Garbage collection is a process which removes dead objects from Java Heap space and returns memory back to Heap in Java.

 

OutOfMemoryError in Java Heap

When JVM starts JVM heap space is equal to the initial size of Heap specified by -Xms parameter, as application progress more objects get created and heap space is expanded to accommodate new objects. JVM also run garbage collector periodically to reclaim memory back from dead objects. JVM expands Heap in Java some where near to Maximum Heap Size specified by -Xmx and if there is no more memory left for creating new object in java heap , JVM throws java.lang.OutOfMemoryError and your application dies. Before throwing the error, JVM tries to run garbage collector to free any available space but even after that not much space available on Heap in Java it results into OutOfMemoryError.

To resolve this error you need to understand your application object profile i.e. what kind of object you are creating, which objects are taking how much memory etc.

Oracle level.....