How to debug OutOfMemoryError

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JVM can crash with OOM Error for multiple reasons.

• Where to check
  • Check in the application logs for OutOfMemoryError

   Exception in thread “xxx" java.lang.OutOfMemoryError: Java heap space

• OutOfMemoryError types
  • Java heap space
  • PermGen space
  • Out of swap space
  • unable to create new native thread
  • Requested array size exceeds VM limit
  • GC overhead limit exceeded

• How to debug different OutOfMemory errors
  • Java heap space
  • GC overhead limit exceeded
    • Happens due to a memory leak.
    • Heap dumps are automatically generated at 70/80/90/98% thresholds of the heap size.
      • file name looks like heapDump_MIVR_70%Threshold.hprof.
    • When the application goes OOM, JVM generates a heap dump during the crash.
      • file name looks like java_pid2665.hprof.
      • Due to a bug CSCte90486, this file can be collected only using remote account.
    • Collect the heap dumps (present in the service log directory. i.e. MIVR directory for engine heap dumps).
    • Collect the thread dump present in JVM.log file.
    • Refer How to analyze heap dumps for the procedure to analyze a heap dump.

• • PermGen space
    • Happens most probably due to ClassLoader leak.
    • When the application goes OOM, JVM generates a heap dump during the crash.
      • file name looks like java_pid2665.hprof.
      • Due to a bug CSCte90486, this file can be collected only using remote account.
    • Collect the heap dumps.
    • Collect the thread dump present in the JVM.log file.

• • Out of swap space
    • Happens due to a memory leak in the JNI code, or in some native applications.
    • System is low on memory.
    • Collect the Perfmon counters of all the services running in the system.
    • Plot a graph of memory usage and find which process is the culprit.

• • unable to create new native thread
    • Happens when OS runs out of system resources, or the application has run out of its address space due to excessive threads.
    • Collect the thread dump present in the JVM.log file.
    • Debug the perfmon logs to find the faulty application.

• • Requested array size exceeds VM limit
    • Happens due to an application bug or a memory leak.
    • Debug application logs and heap dumps if present.