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From Tore Halset <>
Subject Re: Memory Management Practices
Date Thu, 13 Aug 2009 19:29:01 GMT

It is hard to tell where the memory problems are without looking at  
the actual used memory. I normally use jmap to dump memory info and  
then jhat on a different computer to analyze the dump.

jmap -dump:live,file=filename pid
jhat -J-Xmx10G filename

Depending on your heap size, jhat may need a lot of memory and cpu.  
That is why I normally copy the file to a separate non-production  

If your memory are filled with cayenne DataRows, then you should look  
at the size of the datarow cache. Both DataRows and CayenneDataObject  
use Maps that need quite a lot of memory, so you should not have too  

  - Tore.

On Aug 13, 2009, at 6:22 PM, Joe Baldwin wrote:

> Background:
> I have been attempting to do as much performance tuning as I can  
> given the visibility of the middleware I am using, but am running  
> into severe "out of memory" errors with Tomcat on my production  
> server.  My current theory is that I may have missed something  
> concerning how to properly maintain my Cayenne data objects.
> Configuration:
> 1. I am using the most recent version of Cayenne.
> 2. This is primarily a web app, using JSP, Tomcat, Cayenne and MySQL
> 3. Tested both on OSX and Linux
> 4. Essentially, it is a webstore with a lot of products
> 	- small amount of UPDATES
> 	- very large amount of searches resulting in result sets that will  
> average between 50-500 products for read-only
> 	- occasional large result sets of a few thousand products for read- 
> only
> 5. The design is a simple 3-tier.
> After a few hours to a few days of what appears to be very light  
> usage, Tomcat reports "out of memory" errors.  Since the vast  
> majority of the tasks performed by the app are funneled through  
> Cayenne, I am assuming that is where I am making the mistake.
> Question:
> What is the best way to manage the data objects in this  
> configuration?   (i.e. caching, releasing memory, etc)
> Note:
> I was researching the Java Library ArrayList (which I believe is the  
> work-horse for the Cayenne result sets), and there are many  
> recommendations concerning custom clearing of the list and releasing  
> memory.   Is this possibly where I am may have missed something?
> Thanks,
> Joe

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