How many Bytes should I keep memory for running our Module on WAS?

[Former Member]

Hi

We use EP60 on WAS640 SP11.

According to some Help, we need from 512Mb to 1Gb as heap size memory in order to run EP and WAS-Java.

Now,I have 2 questions.

1)Does this mean that we can't give more than 1Gb memory

to JVM(e.g. server0)?! Even if we prepare a server of 4Gb

memory, we can't give over 1Gb memory to one instance ?!

2)I think that clustering architect is good for system to which many users access because of load-balance.And we

want to run many our add-on module on WAS-Java.So,,,

Is this clustering also good in order to run many add-on modules(accessing to R/3 with Jco) on WAS ?

Is there any limitation(e.g. memory size which our module can use)in developing add-on program with Java?

BestRegards

[swapan_saha]

Hi Toshiya,

Theoretically, you can choose maximum heap size (-Xmx) to 4GB or higher in WAS6.40SP11 which uses JDK1.4.2_x. However, for earlier version, SAP J2EEngine 6.20 uses JDK1.3.1_x which only can use maximum heap in the range of 1.3GB - 1.6GB on Windows.

Memory is recycled by Garbage Collection (GC) within JVM. If you have larger heap, it will take longer for GC events. Longer GCs will create larger pauses and increased end response time during the GCs. Moreover, the scalability of the server will be limited as GC puts all threads in the safe state and only one CPU works during the GC. To optimize GC with smaller duration, it is advisable to have multiple instances on the same hardware than a single instance with very large memory for server.

To understand more about JVM memory settings and GC, please read any article from your JVM vendor. For an example, if you use Sun JDK, you can read http://java.sun.com/docs/hotspot/gc1.4.2/index.html

Thanks,

Swapan