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Too much variation in available heap size.

Hi Team,

We are seeing too much variation in available heap size. Let me explain to you our architecture in brief.

Our complete application is divided into 6 PUs. among 3 different applications

1) Core

2) Outbound

3) Inbound

Core app has 2 PUs

 a) Core Pu -> This is an embedded space pu, whose purpose is to process the incoming space documents.
 b) Mirror PU

Outbound app has 3 Pu

 a) DS0 -> Takes data from core pu, converts into some internal format writes back to core space
 b) DS1 -> Takes converted data from space and persists to DB
 c) DS2 -> Takes data from core space and dumps in to flat file

Inbound app has 1 Pu

 a) Welcome -> Takes data from another space and write to the core Pu

We have 4 GSCs with 4 GB heap size. Requirement is that we get data at around 5pm everyday we process and maintain 2 days data in our space.

Now what we have observed is that once the completed data is processed, no more input is coming, no more output is generated. We can see that there are no transactions running but if i see the heap of each GSC, it varies a lot. It climbs uptio 3GB then after a minute it will drop to 1GB and then again it will rise to 3GB and come back to 1 GB.

Since the space is ideal, only thing thats running is our polling containers nothing else, so i am not sure what is causing the huge variation. I dont know if GS does something internal on its own or is it something we are doing, i checked the GSC logs our app logs, nothing is in process but still GSC heap size varies a lot.

It would be great if you could provide some directions or any suggestions where to proceed ??

Thanks a lot :)

asked 2015-10-01 05:50:59 -0500

Harvey gravatar image
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shay hassidim gravatar imageshay hassidim ( 2018-06-30 04:33:54 -0500 )edit

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The space perform many things in the background. Even if your code is not doing anything , there are periodic clean up and other things the space performs. These might generate some floating objects that will be eventually cleared by the garbage collector. If you want these to be cleaned sooner you will have to tune the JVM garbage collection settings.If you run polling containers these will periodically perform some activities that will also generate some floating objects that need to be cleaned.

JMX usage is another reason for floating objects generation.

As long as there is no high CPU usage you should not be worried. By default you should see chain saw memory utilization. Its perfectly OK.Please follow the guidelines described here - with heap smaller than 10GB use CMS:


Make sure you have XX:CMSInitiatingOccupancyFraction set. A good number will be 60. This will trigger garbage collection once the JVM heap utilization cross 60% of the heap size.


answered 2015-10-01 06:31:06 -0500

shay hassidim gravatar image

updated 2015-10-01 07:03:30 -0500

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Hi Shay,

Tnx for the quick reponse, just a slight observation CPU usage of only 1 gsc seems to varying, Its not much it goes from 7-8% to 15-16%, back n forth. This is the gsc on which some primay and some backup partitions are deployed and mirror is deployed. I agree that cpu usage is not high but only 1 gsc seems to by varying, not a burning issue on our end but just a observation. I hope its fine.

Harvey gravatar imageHarvey ( 2015-10-01 10:45:01 -0500 )edit

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Asked: 2015-10-01 05:50:59 -0500

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Last updated: Oct 01 '15