These -X options are nonstandard and
subject to change without notice.
For options that take
<size> parameter,
you should suffix the number with "k" or "K" to indicate kilobytes,
"m" or "M" to indicate megabytes, or "g" or "G" to indicate gigabytes.
- -Xaot[:<suboption>,suboption,...]
- Enables the AOT compiler if -Xshareclasses is
also present. For details of the suboptions, see the Diagnostics Guide. See also -Xnoaot. By
default, the AOT compiler is enabled, but it is only active in conjunction
with -Xshareclasses.
- -Xargencoding
- Allows you to put Unicode escape sequences in the argument list.
This option is set to off by default.
- -Xbootclasspath:<directories and .zip or .jar files
separated by : >
- Sets the search path for bootstrap classes and resources. The
default is to search for bootstrap classes and resources in the internal
VM directories and .jar files.
- -Xbootclasspath/a:<directories and .zip or .jar files
separated by : >
- Appends the specified directories, .zip, or .jar files to the
end of bootstrap class path. The default is to search for bootstrap
classes and resources in the internal VM directories and .jar files.
- -Xbootclasspath/p:<directories and .zip or .jar files
separated by : >
- Prepends the specified directories, .zip, or .jar files to the
front of the bootstrap class path. Do not deploy applications that
use the -Xbootclasspath: or -Xbootclasspath/p: option
to override a class in the standard API, because such a deployment
contravenes the Java™ 2 Runtime Environment binary
code license. The default is to search for bootstrap classes and resources
in the internal VM directories and .jar files.
- -Xcheck:jni
- Performs additional checks for JNI functions. You can also use -Xrunjnichk.
By default, no checking is performed.
- -Xcheck:nabounds
- Performs additional checks for JNI array operations. You can
also use -Xrunjnichk.
By default, no checking is performed.
- -Xcodecache<size>
- Sets the unit size of which memory blocks are allocated to store
native code of compiled Java methods.
An appropriate size can be chosen for the application being run. By
default, this is selected internally according to the CPU architecture
and the capability of your system.
- -Xdbg:<options>
- Loads debugging libraries to support the remote debugging of
applications. Specifying -Xrunjdwp provides
the same support. By default, the debugging libraries are not loaded,
and the VM instance is not enabled for debug.
- -Xdbginfo:<path to symbol file>
- Loads and passes options to the debug information server. By
default, the debug information server is disabled.
- -Xdisablejavadump
- Turns off javadump generation on errors and signals. By default,
javadump generation is enabled.
- -Xfuture
- Turns on strict class-file format checks. Use this flag when
you are developing new code because stricter checks will become the
default in future releases. By default, strict format checks are disabled.
- -Xint
- Makes the JVM use only the Interpreter, disabling the Just-In-Time
(JIT) compiler. By default, the JIT compiler is enabled.
- -Xiss<size>
- Sets the initial Java thread
stack size. 2 KB by default.
- -Xjit[:<suboption>,suboption,...]
- Enables the JIT. For details of the suboptions, see theDiagnostics Guide. See also -Xnojit. By
default, the JIT is enabled.
- -Xlinenumbers
- Displays line numbers in stack traces, for debugging. See also -Xnolinenumbers.
By default, line numbers are on.
- -Xlp<size>
- Requests the JVM to allocate the Java heap
(the heap from which Java objects
are allocated) with 16 MB large pages, if a size is not specified.
If large pages are not available, the Java heap
is allocated with AIX's standard 4 KB pages. AIX® requires
special configuration to enable large pages. For more information
on configuring AIX support for large pages, see http://www.ibm.com/servers/aix/whitepapers/large_page.html.
The SDK uses shmget() with the SHM_LGPG and SHM_PIN flags to allocate
large pages. By default, large pages are not used.
The options
available for
<size> are:
- -Xlp4K
- -Xlp64K (AIX v5.3 and later)
- -Xlp16M (AIX v5.2 and later)
- -Xlp16G (AIX v5.3 and later)
- -Xmca<size>
- Sets the expansion step for the memory allocated to store the
RAM portion of loaded classes. Each time more memory is required to
store classes in RAM, the allocated memory is increased by this amount.
By default, the expansion step is 32 KB.
- -Xmco<size>
- Sets the expansion step for the memory allocated to store the
ROM portion of loaded classes. Each time more memory is required to
store classes in ROM, the allocated memory is increased by this amount.
By default, the expansion step is 128 KB.
- -Xmso<size>
- Sets the C stack size for forked Java threads.
By default, this option is set to 32 KB on 32-bit platforms and 256
KB on 64-bit platforms.
- -Xmx<size>
- Sets maximum Java heap size.The
default is 64 MB.
- -Xnoaot
- Disables the AOT (Ahead-of-time) compiler. See also -Xaot. By default,
the AOT compiler is enabled, but it is only active in conjunction
with -Xshareclasses.
- -Xnojit
- Disables the JIT compiler. See also -Xjit.
By default, the JIT compiler is enabled.
- -Xnolinenumbers
- Disables the line numbers for debugging. See also -Xlinenumbers.
By default, line number are on.
- -Xnosigcatch
- Disables JVM signal handling code. See also -Xsigcatch.
By default, signal handling is enabled.
- -Xnosigchain
- Disables signal handler chaining. See also -Xsigchain.
By default, the signal handler chaining is enabled.
- -Xoptionsfile=<file>
- Specifies a file that contains JVM options and defines. By default,
no option file is used.
- -Xoss<size>
- Sets the Java stack size and C stack size
for any thread. This option is provided for compatibility and is equivalent
to setting both -Xss and -Xmso to
the specified value.The default is 400® KB.
- -Xquickstart
- Improves startup time by delaying JIT compilation and optimizations.
By default, quickstart is disabled and there is no delay in JIT compilation.
- -Xrdbginfo:<host>:<port>
- Loads and passes options to the remote debug information server.
By default, the remote debug information server is disabled.
- -Xrealtime
- Runs the JVM in a real-time mode. In particular, it will run with
-Xgcpolicy:metronome
- -Xrs
- Disables
signal handling in the JVM. Setting -Xrs prevents
the Java runtime from handling any internally or externally generated
signals such as SIGSEGV and SIGABRT.
Any signals raised are handled by the default operating system handlers.
For more information on how the VM makes full use of operating system
signals, see the Diagnostics Guide.
- -Xrun<library name>[:options]
- Loads helper libraries. To load multiple libraries, specify it
more than once on the command line. Examples of these libraries are:
- -Xrunhprof[:help] | [:<option>=<value>,
...]
- Performs heap, CPU, or monitor profiling. For more information,
see the Diagnostics Guide.
- -Xrunjdwp[:help] | [:<option>=<value>,
...]
- Loads debugging libraries to support the remote debugging of
applications. This is the same as -Xdbg.
For more information, see the Diagnostics Guide.
- -Xrunjnichk[:help] | [:<option>=<value>,
...]
- Performs additional checks for JNI functions, to trace errors
in native programs that access the JVM using JNI. For more information,
see the Diagnostics Guide.
- -Xscmx<size>[k|m|g]
- For details of -Xscmx, see Class data sharing command-line options.
- -Xsigcatch
- Enables VM signal handling code. See also -Xnosigcatch.
By default, signal handling is enabled
- -Xsigchain
- Enables signal handler chaining. See also -Xnosigchain.
By default, signal handler chaining is enabled.
- -Xsoftrefthreshold<number>
- Sets the number of GCs after which a soft reference will be
cleared if its referent has not been marked. The default is 3, meaning
that on the third GC where the referent is not marked the soft reference
will be cleared.
- -Xss<size>
- Sets the maximum Java stack
size for any thread. The
default is 512 KB.
- -Xthr:<options>
- Sets the threading options.
- -Xverify
- Enables strict class checking for every class that is loaded.
By default, strict class checking is disabled.
- -Xverify:none
- Disables strict class checking. By default, strict class checking
is disabled.