IBM User Guide for Java V7 on Windows > Reference > Command-line options

JVM command-line options

Use these options to configure your JVM. The options prefixed with -X are nonstandard.

For options that take a <size> parameter, suffix the number with "k" or "K" to indicate kilobytes, "m" or "M" to indicate megabytes, or "g" or "G" to indicate gigabytes.

For options that take a <percentage> parameter, use a number from 0 to 1. For example, 50% is 0.5.

Options that relate to the JIT are listed under JIT and AOT command-line options. Options that relate to the Garbage Collector are listed under Garbage Collector command-line options.

-X	Display help on nonstandard options.
-Xaggressive	Enable performance optimizations.
-Xargencoding	Include Unicode escape sequences in the argument list.
-Xbootclasspath	Set the search path for bootstrap classes and resources.
-Xcheck	Run checks during JVM startup, such as memory checks or checks on JNI functions.
-Xclassgc	Enable dynamic unloading of classes by the JVM.
-Xcompressedrefs	Enable the use of compressed references.
-Xdiagnosticscollector	Enable the Diagnostics Collector.
-Xdisablejavadump	Turns off Javadump generation on errors and signals.
-Xdump	See "Using dump agents" for more information.
-Xenableexplicitgc	Tell the VM to trigger a garbage collection when a call is made to System.gc().
-Xfastresolve	Tune performance by improving the resolution time for classes.
-Xfuture	Turns on strict class-file format checks.
-Xiss	Set the initial stack size for Java threads.
-Xjarversion	Produces output information about the version of each .jar file.
-Xjni	Set JNI options.
-Xlinenumbers	Display line numbers in stack traces for debugging.
-Xlockword	Test whether performance optimizations are negatively impacting an application.
-Xlog	Enable message logging.
-Xlp	Requests the JVM to allocate the Java object heap with large pages.
-Xmso	Set the initial stack size for operating system threads.
-Xnoagent	Disable support for the old JDB debugger.
-Xnoclassgc	Disable dynamic class unloading.
-Xnocompressedrefs	Disable the use of compressed references.
-Xnolinenumbers	Disable the line numbers for debugging.
-Xnosigcatch	Disable JVM signal handling code.
-Xnosigchain	Disable signal handler chaining.
-Xoptionsfile	Specifies a file that contains JVM options and definitions.
-Xoss	Set the maximum Java stack size for any thread.
-Xrdbginfo	Loads the remote debug information server with the specified host and port.
-Xrs	Disable signal handling in the JVM.
-Xscdmx	Use the -Xscdmx option to control the size of the class debug area when creating a shared class cache.
-Xscmx	Specifies cache size.
-Xshareclasses	Enable class sharing.
-Xsigcatch	Enable VM signal handling code.
-Xsigchain	Enable signal handler chaining.
-Xss	Set the maximum stack size for Java threads.
-Xssi	Set the stack size increment for Java threads.
-Xthr
-XtlhPrefetch (64-bit)	Speculatively prefetches bytes in the thread local heap (TLH) ahead of the current allocation pointer during object allocation.
-Xtrace	Trace options.
-Xtune:elastic	Turn on JVM function that accommodates changes in the machine configuration dynamically at run time.
-Xtune:virtualized	Optimizes JVM function for virtualized environments, such as a cloud.
-Xverify	Use this option to enable or disable the verifier.
-Xzero	Enable reduction of the memory footprint of the Java runtime environment when concurrently running multiple Java invocations.

Parent: Command-line options

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