jvm-arguments

In a shell script, I have set the JAVA_OPTS environment variable (to enable remote debugging and increase memory), and then I execute the jar file as follows: export JAVA_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n -Xms512m -Xmx512m" java -jar analyse.jar $* But it seems there is no effect of the JAVA_OPTS env variable as I cannot connect to remote-debugging and I see no change in memory for the JVM. What could be the problem? PS: I cannot use those settings in the java -jar analyse.jar $* command because I process command line arguments in the application. I

I am wondering is it possible to log every exception which occurs on JVM level without changing application code? By every exception I mean caught and uncaught exception... I would like to analyze those logs later and group them by exception type (class) and simply count exceptions by type. I am using HotSpot ;) Maybe there is smarter why of doing it? For example by any free profiler (YourKit has it but it is not free)? I think that JRockit has exception counter in management console, but don't see anything similar for HotSpot. I believe there are free tools to do it, but even making your own

I've kind of asked this question before - What does JVM flag CMSClassUnloadingEnabled actually do? , but this time it's slightly different! If I start a Java VM with the -XX:+CMSPermGenSweepingEnabled flag set, the following message is printed: Please use CMSClassUnloadingEnabled in place of CMSPermGenSweepingEnabled in the future The -XX:+CMSPermGenSweepingEnabled flag is often used to mitigate against PermGen OutOfMemory errors, however I have read elsewhere that people have found that by following the above advice they have still had these errors, but by sticking with -XX:

The theoretical maximum heap value that can be set with -Xmx in a 32-bit system is of course 2^32 bytes, but typically (see: Understanding max JVM heap size - 32bit vs 64bit ) one cannot use all 4GB. For a 64-bit JVM running in a 64-bit OS on a 64-bit machine, is there any limit besides the theoretical limit of 2^64 bytes or 16 exabytes? I know that for various reasons (mostly garbage collection), excessively large heaps might not be wise , but in light of reading about servers with terrabytes of RAM, I'm wondering what is possible . If you want to use 32-bit references, your heap is limited

Specifically, why would it help to fix a PermGen OutOfMemoryError issue? Also, bonus points for an answer that points me to the documentation on JVM arguments... The permanent space is where the classes, methods, internalized strings, and similar objects used by the VM are stored and never deallocated (hence the name). This Oracle article succinctly presents the working and parameterization of the HotSpot GC and advises you to augment this space if you load many classes (this is typically the case for application servers and some IDE like Eclipse) : The permanent generation does not have a