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BEA JRockit 1.4.2 SDK Frequently Asked Questions

This page answers some frequently asked questions about BEA JRockit.

- On which platforms can I run JRockit?
- Where do I find published benchmark figures?
- I am trying to start JRockit, but I get this error message: `C:\java\jrockit-j2sdk1.4.2_04\bin>java -XXnoopt -version Unknown option or illegal argument: -XXnoopt.` What do I need to do?
- I suspect that my application has a memory leak, what do I do?
- How can I monitor my running application?
- I get the error message:`Could not create the Java virtual machine.` What do I need to do?
- How do I perform a JRA-recording?
- Which garbage collection algorithm should I use for my application?
- Does dynamic optimization conflict with my application?
- Does JRockit support PAE?
- Where can I find a forum where I can discuss my experiences with JRockit?

On which platforms can I run JRockit?

On the Supported Platforms page, you find a complete list of all platforms JRockit supports.

Where do I find published benchmark figures?

On Standard Performance Evaluation Corporation you can find recent and relevant benchmarking figures.

I am trying to start JRockit, but I get this error message:`C:\java\jrockit-j2sdk1.4.2_04\bin>java -XXnoopt -version Unknown option or illegal argument: -XXnoopt.` What do I need to do?

You need to set a valid startup option. See the Command Line Options document for the available startup options. You can also look in the document Tuning BEA JRockit 1.4.2 JVM for more information on how to best tune your JVM.

I suspect that my application has a memory leak, what do I do?

You can use the new BEA JRockit Memory Leak Detector tool to see where you application might leak memory. See Using the BEA JRockit Memory Leak Detector for how you can use this tool.

How can I monitor my running application?

BEA JRockit is delivered with a built-in monitoring tool called BEA JRockit Management Console. For information on how to use the Managagement Console, see Using the BEA JRockit Management Console.

I get the error message: `Could not create the Java virtual machine.` What do I need to do?

Please check the spelling of the startup options that you have set. If you still cannot start the JVM, look in the Command Line Options document for the available startup options. You can also look in the document Tuning BEA JRockit 1.4.2 JVM for more information on how to best tune your JVM.

How do I perform a JRA-recording?

A JRockit Runtime Analyzer (JRA) recording is a way for you to study the performance of JRockit for a set time period. For information on how to use the tool, see Using the BEA JRockit Runtime Analyzer. This tool is installed separately from the JVM.

Which garbage collection algorithm should I use for my application?

Finding the correct garbage collector requires that you know how your application behaves. For thorough information on how to best find a garbage collector algoithm for your application, see Using the BEA JRockit 1.4.2 Memory Management System.

Does dynamic optimization conflict with my application?

The dynamic optimization is done in parallell with the rest of the code generation. This means that there really is no conflict with the running of your application. Most code pieces are not optimized, since that takes too many resources from the code generation.

Does JRockit support PAE?

Physical Address Extension (PAE) provides the possibility to map physical memory into your process virtual memory address space. At any given time, you can still have just 2 GB mapped (3 GB with the /3GB option); that is, you have to re-use a portion of the virtual address space to map different portions of the physical address space. Therefore you cannot simply address more memory with regular pointers. This does not work well with a normal Java heap, which uses 32-bit pointers to reference objects and needs the entire heap in the virtual address space at all times.

PAE works well with applications that can jointly control mapping and memory access. At this point this is not well suited for Java. However a native database driver might use PAE to cache data. You should discuss with the various database vendors how to make this happen (if it is not available already). You might even create a custom cache by rolling your own “DB access layer” on top of a native database API using JNI.

Other ways of using your plentiful physical memory includes using several Java processes (each Windows process can get 2 GB physical memory to use for its private address space).

If you a need a larger Java heap, you need to use a 64-bit implementation of BEA JRockit; that is, the IA-64 versions for Windows 2003 or Linux.

Where can I find a forum where I can discuss my experiences with JRockti?

BEA provides a developer newsgroup on http://forums.bea.com/bea/forum.jspa?forumID=2009.