Java VM Settings to avoid memory leaks

[Former Member]

hello gurus,

we have currently a few memory problems with our netweaver AS Java. Once a week our server dies because of "return code 666: out of memory". We are using a netweaver AS Java 640 on an Windows 2003 x64 Server. It is a dedicated machine with 16 GB Ram. The memory settings in the JVM are:

-Xms4096M

-Xmx4096M

-Xss2M

-XX:+DisableExplicitGC

-XX:+PrintGCDetails

-XX:+PrintGCTimeStamps

-XX:+UseParNewGC

-XX:+UseTLAB

-XX:CodeCacheMinimumFreeSpace 2M

-XX:CompilerThreadStackSize 4096

-XX:MaxNewSize 682m

-XX:MaxPermSize 2048m

-XX:NewSize 682m

-XX:PermSize 2048m

-XX:ReservedCodeCacheSize 64M

-XX:SoftRefLRUPolicyMSPerMB 1

-XX:SurvivorRatio 2

-XX:TargetSurvivorRatio 90

We are running our b2b Shop on this server. I don´t know if the 4 GB are enough Memory for Java since we have 16 GB available within our machine. But I´d like to know if i can just increase the Heap Size to 8GB or more.

I´m looking forward to hear your recommendations.

best regards

Tobias

[rakeshjogi]

JVM settings alone cannot prevent memory leaks. However, JVM settings can influence the timeframe in which memory problems can arise. In a dedicated NetWeaver AS Java system with 16 GB of physical memory, using a 4 GB Java heap is relatively conservative. If there is sufficient memory available in your operating system,  then in that case, you can go ahead and try increasing  the heap size to 6-8 GB. However, a recurring out-of-memory condition indicates a likely heap or off-heap memory leak rather than simply insufficient heap size. Analyzing GC logs to verify whether old generation memory is reclaimed after a Full GC and capturing heap dumps to identify retained objects are essential steps. Proper diagnosis and fixing the underlying cause is more effective than relying solely on JVM memory tuning to avoid memory leaks.  For a deeper understanding of common signs of a Java memory leak, identifying memory leaks by analyzing a heap dump, check out this blog,  From Symptoms to Solutions: Troubleshooting Java Memory Leaks & OutOfMemoryError.