what does JVM do?

• Learn about JVM internals - what does the JVM do?

http://www.youtube.com/watch?v=UwB0OSmkOtQ

• Java Programming Tutorial 2: Java Virtual Machine (JVM) : How it works

http://www.youtube.com/watch?v=aa7Y07Wv1-M

• JVM parameters in Java

1)    JVM Options that begin with -X are non-standard (thy are not guaranteed to be supported on all JVM implementations), and are subject to change without notice in subsequent releases of the JDK.

2)    JVM Options or parameters which are specified with -XX are not stable and are not recommended for casual use.

Good knowledge of JVM options specially related to GC tuning is important for time critical application e.g. high volume low latency electronic trading platform where every micro seconds matter

1)    Boolean JVM options can be  turned on with -XX:+ and can be turned off with -XX:-.

2)    Numeric JVM Options can be set with -XX:=. Numbers can include 'm' or 'M' for megabytes, 'k' or 'K' for kilobytes, and 'g' or 'G' for gigabytes (for example, 32k is the same as 32768).

3)    String JVM options can be set by using -XX:=, and usually used to specify a file, a path, or a list of commands.

1) JVM memory options related to java heap size

Following three JVM options are used to specify initial and max heap size and thread stack size while running Java programs.

 -Xms        set initial Java heap size

 -Xmx        set maximum Java heap size

 -Xss>         set java thread stack size

 

 http://javarevisited.blogspot.com/2011/11/hotspot-jvm-options-java-examples.html