How to increase JVM Process size for WebLogic running SOA Applications.

Question

Hi,
I believe 32 Bit OS can address up to 4GB memory so theoretically 32 Bit JVM can use 4GB but practical convention is 2GB as other 2GB is used by OS itself and also this default JVM Process size is set somewhere and I also believe that if JVM is 32 bit on 64Bit OS even though JVM will run on 32Bit Virtual Machine so JVM does not know that it is 64Bit OS in that case again it can use max Process default size up to 2GB.
And for 64Bit JVM, I can allocate more than 4GB depend on my available RAM size to Xmx, MaxPermSize parameters in java.exe file and after that I can set the same value in “setSOADomainEnv.cmd” or to “setDomainEnv.cmd” file.
But I am 99% sure by just assigning more memory value to Xmx, MaxPermSize in “setSOADomainEnv.cmd” file only won’t work (not setting Xmx in java.exe), if it would have worked then in my case when I was assigning 1536 to Xmx in “setSOADomainEnv.cmd” file then why it was showing out of memory error. I think that is because it was only taking default 2GB for my 32 Bit JVM not considering 3GB or 4GB. So i think i have to change default memory size what JVM can use (<http://www.wikihow.com/Increase-Java-Memory-in-Windows-7> but i am using windows 8 so for that I don’t know the option to change this default Process Size)
I also believe that first JVM start and before start it check how much memory it can use from it’s own –Xmx parameter in some ware configuration or java.exe file and after that it allocate that much size of JVM Process Memory in RAM then after it loads Weblogic or Java Applications in its (Heap + Non-heap + Native Area) which are parts of JVM Process memory
I read post on :< http://stackoverflow.com/questions/3143579/how-can-jvm-use-more-than-4gb-of-memory > and < http://alvinalexander.com/blog/post/java/java-xmx-xms-memory-heap-size-control >
All used  : 
java -Xmx64m -classpath ".:${THE_CLASSPATH}" ${PROGRAM_NAME}
java –Xmx6g     //command which will call java/JVM interpreter which will hold –Xmx parameter to set Heap size for JVM
                                before JVM comes in memory (JVM process memory)
now my question is can I manually open any configuration file or java.exe same like “setSOADomainEnv.cmd” or “setDomainEnv.cmd” (I know since java.exe is exe I can’t open simply but I want similar work around)
so that I don’t need to type java –Xmx6g every time when I run weblogic (and then later I can change weblogic “setDomainEnv.cmd” Xmx and PermSize to more than default size 4GB to 5GB or 6GB in the case of 64Bit OS)
Please correct me if I am wrong in my understanding.
Thanks.

Answer 1

These days the VM will detect a "server" machine and set up the memory appropriate for that.
You can create a simple java console application and have it print the memory settings (find the appropriate java class fort that.)
There is of course the possibility that your application is running out of memory because it is doing something wrong and not because the VM doesn't have enough memory.  You can force that in a test setup by LOWERING the maximum amount of memory and thus making it more likely that an out of memory exception will occur.