This is rather a Java than a tomcat question: The JVM allocates memory based on whatever default your current JVM version decides (you don't mention what version of Java you're on)
>From a text on http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonomics.html that's linked from my Java's manpage: *initial heap size* Larger of 1/64th of the machine's physical memory on the machine or some reasonable minimum. Before J2SE 5.0, the default initial heap size was a reasonable minimum, which varies by platform. You can override this default using the |-Xms| command-line option. *maximum heap size* Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0, the default maximum heap size was 64MB. You can override this default using the |-Xmx| command-line option. *Note:* The boundaries and fractions given for the heap size are correct for J2SE 5.0. They are likely to be different in subsequent releases as computers get more powerful. Note that this is from JavaSE7 and even mentions 5 - with more power there comes more initial and maximum memory defaults. I'm not aware of the actual development of the default memory - mostly because I consider it good practice to know what an application uses and provide it explicitly, rather than relying on defaults. (and frankly, on the applications that I see, the default typically is not even enough - let alone a good basis for tuning) While we're at it: For production systems I consider it good practice to set -Xms and -Xmx to the same value. Reason: If you don't have enough memory available, you want to know this when the process starts, not days later when it tries to allocate "the rest" - typically sunday night at 3am. Olaf Am 21.02.2016 um 03:39 schrieb Gokul.Baskaran: > Hi, > > I am currently running tomcat 7 in Windows 2012. > > The current JVM Heap memory parameters are set to empty, does the JVM Heap > memory utilize the entire memory of the OS or does it default to a specific > memory number? > > Thank you > -Gokul > >
