What does Java option -Xmx stand for? [duplicate]

java -Xmx1024m filename

what does -Xmx mean?

3

5 Answers

see here: Java Tool Doc, it says,

-Xmxn
Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 64MB. The upper limit for this value will be approximately 4000m on Solaris 7 and Solaris 8 SPARC platforms and 2000m on Solaris 2.6 and x86 platforms, minus overhead amounts. Examples:

 -Xmx83886080 -Xmx81920k -Xmx80m

So, in simple words, you are setting Java heap memory to a maximum of 1024 MB from the available memory, not more.

Notice there is NO SPACE between -Xmx and 1024m

It does not matter if you use uppercase or lowercase. For example: "-Xmx10G" and "-Xmx10g" do the exact same thing.

7

C:\java -X -Xmixed mixed mode execution (default) -Xint interpreted mode execution only -Xbootclasspath:<directories and zip/jar files separated by ;> set search path for bootstrap classes and resources -Xbootclasspath/a:<directories and zip/jar files separated by ;> append to end of bootstrap class path -Xbootclasspath/p:<directories and zip/jar files separated by ;> prepend in front of bootstrap class path -Xnoclassgc disable class garbage collection -Xincgc enable incremental garbage collection -Xloggc:<file> log GC status to a file with time stamps -Xbatch disable background compilation -Xms<size> set initial Java heap size -Xmx<size> set maximum Java heap size -Xss<size> set java thread stack size -Xprof output cpu profiling data -Xfuture enable strictest checks, anticipating future default -Xrs reduce use of OS signals by Java/VM (see documentation) -Xcheck:jni perform additional checks for JNI functions -Xshare:off do not attempt to use shared class data -Xshare:auto use shared class data if possible (default) -Xshare:on require using shared class data, otherwise fail.
The -X options are non-standard and subject to change without notice.

2

The -Xmx option changes the maximum Heap Space for the VM. java -Xmx1024m means that the VM can allocate a maximum of 1024 MB. In layman terms this means that the application can use a maximum of 1024MB of memory.

5

Max heap Usage for the application is is 1024 MB

-Xmx sets the Maximum Heap size