Wednesday, 15 April 2015

How to manually generate a Heapdump in WebSphere on Windows

Problem(Abstract)

How to generate a heapdump without waiting for an OutOfMemoryError condition to occur.

Resolving the problem

Occasionally a heapdump needs to be generated without waiting for an OutOfMemoryError condition to occur. 

For example: an OutOfMemoryError will probably cause a system outage. On a production system this is not a desired event. If we manually create a heapdump before the OutOfMemoryError generates one, then the application server can be recycled and we will get a heapdump without an unscheduled outage. 

The manually generated heapdump will not be as useful as one which was generated by an OutOfMemoryError, but sometimes it can be of some use. The longer we can wait before generating the heapdump, the more likely the heapdump will contain the objects causing the OutOfMemory. If the heapdump is generated too soon, the largest memory user is not likely to be the same largest memory user when the heap is completely full.



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