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In weblogic JRockit, sometimes the heap gets full (usage reaches the heap max size 4096M). However, after we dump the heap, the dump file size is only 200~ 300M. This it is strange, and on top of that we can not identify what objects occupy the heap through EMA tool.

Has anyone experienced similar and does someone know the JRockit heap dump mechanism?

Mad Physicist
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zhengel
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  • this is the normal behavior of jrockit. A full gc is performed before creating the heap dump. If you suspect a memory leak, take serveral heap dumps during a load test and analyze them with apropriate tools such as Eclipse MAT. – Emmanuel Collin Jun 07 '16 at 07:25
  • thanks Emmanuel sharing. The problem was identified and it is related with JRockit. You can refer to Oracle blog [https://blogs.oracle.com/buck/entry/where_did_all_of_these](https://blogs.oracle.com/buck/entry/where_did_all_of_these) – zhengel Jun 14 '16 at 03:55

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Whenever you take heap dump a full GC will run and then heap will be dumped. May be that's the reason your heap dump size is very small.

If you want to analyze memory leak between Full GCs, then probably memory profilingusing a Java profiler (Mission Control, jProfiler, etc) is your only option.

Naveen Hiremath
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