Hi Websphereians,

plz help me out with the following terms regarding Thread & Heap dumps :

1)  xdump
2)  jmap
3) difference between memory dump, java dump, JVM dump


also with the usage of the following commands:

1)   -Xdump:heap:events=user
       -Xdump:system:events=user
       -Xdump:java+heap+system:events=user

2)   java -Xdump:heap:events=vmstop,file=my.dmp

3)   java -Xms256m -Xmx512m MyClass

4)  gdb --pid=[java pid]
gcore [file name]
detach
quit
jmap -heap:format=b [java binary] [core dump file]


             please............. Thank you.
 

[quote author=197104241 post=531393669]Hi Websphereians,

plz help me out with the following terms regarding Thread & Heap dumps :

My point of view


1)  xdump
     The -Xdump option controls the way you use dump agents and dumps
    publib.boulder.ibm.com/infocenter/javasd...

2)  jmap
    jmap prints shared object memory maps or heap memory details of a given process or core file or a remote debug server. If the given process is running on a 64-bit VM, you may need to specify the -J-d64 option.
    docs.oracle.com/javase/6/docs/technotes/...

3) difference between

    memory dump=?¿?¿?¿?¿ JVM dump (not sure)

    java dump
    Also called Thread dump)
   Javadump produces files that contain diagnostic information related to the JVM and a Java™ application captured at a point during execution. For example, the information can be about the operating system, the application environment, threads, stacks, locks, and memory.

   The exact contents depend on the platform on which you are running. By default, a Javadump occurs when the JVM terminates unexpectedly. A Javadump can also be triggered by sending specific signals to the JVM. Javadumps are human readable.


    JVM dump(¿heap?)
   Heapdumps produce phd (portable heap dump) format files by default. Not human readable.
   
   The term Heapdump describes the IBM® Virtual Machine for Java™ mechanism that generates a dump of all the live objects that are on the Java heap; that is, those that are being used by the running Java application.

   This dump is stored in a Portable Heap Dump (PHD) file, a compressed binary format. You can use various tools on the Heapdump output to analyze the composition of the objects on the heap and (for example) help to find the objects that are controlling large amounts of memory on the Java heap and the reason why the Garbage Collector cannot collect them.


also with the usage of the following commands:

1)   -Xdump:heap:events=user
      generate a heap dump when The JVM receives the SIGQUIT (Linux®, AIX®, z/OS®, and i5/OS®) or SIGBREAK (Windows®) signal from the operating system.

       -Xdump:system:events=user
       generate a system dump when The JVM receives the SIGQUIT (Linux®, AIX®, z/OS®, and i5/OS®) or SIGBREAK (Windows®) signal from the operating system.

       -Xdump:java+heap+system:events=user
    generate a java, heap and system dumps when The JVM receives the SIGQUIT (Linux®, AIX®, z/OS®, and i5/OS®) or SIGBREAK (Windows®) signal from the operating system.

2)   java -Xdump:heap:events=vmstop,file=my.dmp
      generate a heap dump named my.dump when the virtual machine stops.

3)   java -Xms256m -Xmx512m MyClass
      Execute Myclass with min 256MB and max 512MB heap size.

4) 
     I don't know sure but I think that gdb and gcore are operating system tool to generate a process dump.

 gdb --pid=[java pid]
gcore [file name]
detach
quit
jmap -heap:format=b [java binary] [core dump file]


             please............. Thank you.
 [/quote]


  Hope this helps.

regards

Gabriel, thanks a lot for the work.