Memory management of WEB AS 6.20

[Former Member]

Hello,

has anybody informationen about the memory management of the WEB As 6.20 or the JVM?

How can I see when a garbage collection takes place? How much memory should be allocated by the server nodes?

Best regards

Olaf

[Former Member]

Hi, Olaf.

If you are using JDK 1.4.2.XX, you can see the GC trace with the following settings.

-verbose:gc

-XX:+PrintGCTimeStamps

-Xloggc:<output file for GC trace>

If you want to see more detailed GC trace, add the

-XX:+PrintGCDetail

option also.

If you want to visualize the above output, you can try GCViewer from here.

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

The GCViewer is very simple and easy to use but one problem is that GCViewer cannot parse PrintGCDetail option(That's why i referred to this option separately).

Thanks.

[detlev_beutner]

Hi Seejon,

> If you are using JDK 1.4.2

I hope he is not... he's on 6.20, only supporting 1.3.1

Best regards

Detlev

[Former Member]

Thanks Detlev.

And i'm sorry. i tried only with WAS AS 6.40.

The GCViewer, however, can be used also for JDK 1.3.1 with "-verbose:gc" option only.

GCViewer supports the following formats.

Sun JDK 1.2.2/1.3.1/1.4 with the option -verbose:gc

Sun JDK 1.4 with the option -Xloggc:<file> (preferred)

IBM JDK 1.3.1/1.3.0/1.2.2 with the option -verbose:gc

Best Regards.

[swapan_saha]

I think information provided here is sufficient to analysis GC both at JDK 1.3.1_x and JDK 1.4.2_x. There are also several open source/free tools to graphically view -verbose:gc output. Other than GCViwer, you can try Samurai too.

http://yusuke.homeip.net/samurai/?english#content_1_10

Samurai does bot GC visualization and Java Thread dump analysis.

Thanks,

Swapan

[swapan_saha]

Hi Olaf,

Server nodes are bound by the maximum heap size (-Xmx) value you specify with JVM parameters. Based on the end users activities and the applications you deployed within the WAS, Java process will allocate memory. To find out how much memory is allocated and recycled, you can get some info when you add -verbose:gc with as JVM options. If you see very frequent and long GC (more than few seconds, depends on the "mx" value and other values NewSize, etc.) you need to increase your "mx" value in case you have memory available in the box.

In summary, to have some idea what is going on within the JVM as far as memory is concerned, you can get it from -verbose:gc output.

Thanks,

Swapan

[Benny]

Hi Olaf,

> has anybody informationen about the memory management

> of the WEB As 6.20 or the JVM?

There is an article here on SDN that includes such stuff:

https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/documents/a1-8-4/how to tune sap j2ee engine 6.20.pdf

> How can I see when a garbage collection takes place?

NOT.

> How much memory should be allocated by the server

> nodes?

See the article. Anyway, this is depending on a lot of factors.

Regards,

Benny