Full Garbage Collection Problem

[former_member184114]

Hi All,

We are working on NetWeaver Application Server JAVA 7.0

I am getting an error message in of the the EWA reports for JAVA system. The red alert says as below:

The maximum ratio of full garbage collections to total garbage collections in the reported interval was higher than 90%.

In order to solve the above problem, I increased Heap Memory for all JAVA Server nodes to 3072 (earlier it was 2048 for all the server nodes). However, still I am getting same error in EWA report.

Can any one help me in further analysing and solving the above problem?

Your help is appreciated.

[desiree_matas · Accepted solution]

Hello Faisal,

There are two possibilities here:

-The EWA report is incorrect or:

-There are some performance degradation in the system. Are the users really facing performance issues, bottlenecks or system hanging situations? In that case you should check the garbage collection reports to see how is the system behaving.

Regards,

Désiré

[former_member184114 · Accepted solution]

Hi Desiree,

Thanks for your reply.

I am not sure if the EWA reports is incorrect and also dont know how to verify this either!

Well, users are not facing that performance problem and they never complained of it. I even access our server daily but never felt that the performace is slow; infact very slow.

After increasing the heap memory, this problem from the EWA report has gone as of now.

Regards,

Faisal

[former_member184114]

Thanks all for your help.

It seems this problem is solved for me as of now. What I did was, I increased the HEAP memory for each server node to 3047 MB (earlier it was 2948 MB. In the next run of EWA report, this problem got disappeared.

Thanks all for your support.

Regards,

Faisal

[hemanth2]

Dear Faisal,

Hope you are doing good.

More heap does not mean that the GC goes low. on the othet hand, if heapsize is more, this means more work for the garbage collector. It is always wise to add additional server nodesif there is enough RAM on the machine than increasing the heap.

The rule of thumb for number of server nodes for SUN Java VM with 2 GB Heap each will be #ServerNodes = (AvailableMemory / 2.5 GB).

A cluster restart will be needed after addition of the server node

Thank you and have a nice day :).

_____________

Kind Regards,

Hemanth

SAP AGS

[former_member184114]

Hi Hemanth,

Thanks for your reply and I apoligize for delay in my reply.

I will consider your suggestion and thumb rule in future. However, What I did is, I increased Heap Memory from 2GB to 3GB for each server nodes (total we have 3 server nodes). This, I think solved our problem and now this error in EWA report does not appear.

Thanks,

Regards,

Faisal

[Former Member]

Make sure that you have maintained [SAP recommended JVM parameters|https://service.sap.com/sap/support/notes/723909]

Check std_server0.out and analyse garbage collection information provided.

[former_member184114]

Hi,

May you please tell me how I can analyze GC information in std_server*?

BTW, I have already updated our server with SAP's recommendations for J2EE server.

Regards,

Faisal

[Former Member]

Here are links to some of the tools. I have worked with [IBM GC for IBM JVM|http://www.ibm.com/developerworks/java/library/j-ibmtools2/index.html]. You may have to try others that can read Sun JVM's GC log.

http://www.tagtraum.com/gcviewer.html

http://www.yourkit.com/overview/index.jsp

https://h20392.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=HPJMETER

http://java.sun.com/performance/jvmstat/visualgc.html