JVM Memory increase - Websphere

This is a discussion on JVM Memory increase - Websphere ; Can anyone give me some feedback into possible problems I might encounter from increasing the JVM memory limit....

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Thread: JVM Memory increase

  1. JVM Memory increase

    Can anyone give me some feedback into possible problems I might encounter from increasing the JVM memory limit.

  2. Re: JVM Memory increase

    Hello,

    Possible problems include:

    1) Reduced performance when the garbage collector does a full GC. This is less of a problem on newer versions of the JDK, but the theory goes that the more memory the GC has to sweep, the longer it will take - which means potentially more CPU cycles spent on non-productive work.

    2) Increasing the Java heap size will decrease the amount of "native" memory available. On most 32-bit systems, the maximum process size is 4GB. Some of the 4GB is used in OS and JVM overhead - the rest is split between Java heap and native heap. The native heap is where all native objects (i.e. JNI, native threads, etc.) are stored. Running out of memory in either heap will lead to OutOfMemoryErrors and can cause the process to crash. If your application uses a lot of native code then you will need to strike a balance between the native and Java heaps.

    3) Over-committing the physical memory. If you are using more memory than you have physical memory in the box, then you will page to the disk which can be very expensive in terms of performance.

    That's all that I can think of... :-) Good luck!

    Andy

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