Memory and OutOfMemoryError Issues

When a WebSphere server is started, a specified amount of system memory is allocated for the Java heap. The Java objects created by the running process are allocated a portion of this heap space. In addition, JVMs will allocate memory outside of the heap for threads, classloaders, classes, buffers and native code allocations (c malloc). During the execution of the process, if a Java object cannot be allocated, or if no memory is available for native allocations, an OutOfMemoryError (OOM) will be thrown. The first case is called Java heap exhaustion, and the second case is native memory exhaustion.

The first step in resolving an OutOfMemoryError is determining which type of memory exhaustion is occurring. This is often apparent in the Javacores generated by the error, but sometimes may require additional investigation to make a determination.

Once the problem is identified as either heap or native exhaustion, appropriate steps may be taken to begin debugging.