Deployment Considerations - Sun JVMs

When deploying Coherence on Sun JVMs please be aware of the following:

Heap Sizes

With 1.4 JVMs Coherence recommends keeping heap sizes below 1GB in size per JVM. Multiple cache servers can be used allow a single machine to achieve higher capacities. With Sun's 1.5 JVMs, heap sizes beyond 1GB are reasonable, though GC tuning is still advisable to minimize long GC pauses. See Sun's GC Tuning Guide for tuning details. It is also advisable to run with fixed sized heaps as this generally lowers GC times.


When available Coherence will make use of the highly concurrent AtomicLong class, which allows concurrent atomic updates to long values without requiring synchronization. Sun 1.4 client JVMs include an implementation which is not stable on some multiprocessor systems. If Coherence detects that it is being run on a Sun 1.4 client JVM it will default to a safe but slower synchronized implementation, and will output the following log message.

sun.misc.AtomicLong is not supported on this JVM; using a synchronized counter.

It is suggested that you run your 1.4 JVMs in server mode to ensure that the stable and highly concurrent version can be utilized. To run the JVM in server mode include the -server option on the Java command line.