Default settings for the JVM

IBM User Guide for Java V7 on Windows > Reference

Default settings for the JVM

This appendix shows the default settings that the JVM uses. These settings affect how the JVM operates if you do not apply any changes to its environment. The tables show the JVM operation and the default setting.
These tables are a quick reference to the state of the JVM when it is first installed. The last column shows how the default setting can be changed:

c

The setting is controlled by a command-line parameter only.

e

The setting is controlled by an environment variable only.

ec

The setting is controlled by a command-line parameter or an environment variable. The command-line parameter always takes precedence.

JVM setting Default Setting affected by

Javadumps Enabled ec

Javadumps on out of memory Enabled ec

Heapdumps Disabled ec

Heapdumps on out of memory Enabled ec

Sysdumps Enabled ec

Where dump files are produced Current directory ec

Verbose output Disabled c

Boot classpath search Disabled c

JNI checks Disabled c

Remote debugging Disabled c

Strict conformance checks Disabled c

Quickstart Disabled c

Remote debug info server Disabled c

Reduced signaling Disabled c

Signal handler chaining Enabled c

Classpath Not set ec

Class data sharing Disabled c

Accessibility support Enabled e

JIT compiler Enabled ec

AOT compiler (AOT is not used by the JVM unless shared classes are also enabled) Enabled c

JIT debug options Disabled c

Java2D max size of fonts with algorithmic bold 14 point e

Java2D use rendered bitmaps in scalable fonts Enabled e

Java2D freetype font rasterizing Enabled e

Java2D use AWT fonts Disabled e

JVM setting AIX IBM i Linux Windows z/OS Setting affected by

Default locale None None None N/A None e

Time to wait before starting plug-in N/A N/A Zero N/A N/A e

Temporary directory /tmp /tmp /tmp c:\temp /tmp e

Plug-in redirection None None None N/A None e

IM switching Disabled Disabled Disabled N/A Disabled e

IM modifiers Disabled Disabled Disabled N/A Disabled e

Thread model N/A N/A N/A N/A Native e

Initial stack size for Java™ Threads 32-bit. Use: -Xiss<size> 2 KB 2 KB 2 KB 2 KB 2 KB c

Maximum stack size for Java Threads 32-bit. Use: -Xss<size> 256 KB 256 KB 256 KB 256 KB 256 KB c

Stack size for OS Threads 32-bit. Use -Xmso<size> 256 KB 256 KB 256 KB 32 KB 256 KB c

Initial stack size for Java Threads 64-bit. Use: -Xiss<size> 2 KB N/A 2 KB 2 KB 2 KB c

Maximum stack size for Java Threads 64-bit. Use: -Xss<size> 512 KB N/A 512 KB 512 KB 512 KB c

Stack size for OS Threads 64-bit. Use -Xmso<size> 256 KB N/A 256 KB 256 KB 256 KB c

Initial heap size. Use -Xms<size> 4 MB 4 MB 4 MB 4 MB 4 MB c

Maximum Java heap size. Use -Xmx<size> Half the available memory with a minimum of 16 MB and a maximum of 512 MB 2 GB Half the available memory with a minimum of 16 MB and a maximum of 512 MB Half the available memory with a minimum of 16 MB and a maximum of 512 MB See note. Half the available memory with a minimum of 16 MB and a maximum of 512 MB c

Compressed references Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB Disabled ec

Page size for the Java object heap and code cache. For restrictions, see Configuring large page memory allocation Operating system default Operating system default Architecture:

Linux on x86 and AMD64/EM64T: 2 MB
Linux on System z: 1 MB
Other architectures: operating system default

Operating system default 1M pageable c

Note: For earlier releases of Java, the value of -Xmx for the Windows JVM is half the physical memory with a minimum of 16 MB, and a maximum of 2 GB.
"Available memory" is defined as being the smallest of two values:

The real or "physical" memory.
The RLIMIT_AS value.

Parent: Reference

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JVM setting	Default	Setting affected by
Javadumps	Enabled	ec
Javadumps on out of memory	Enabled	ec
Heapdumps	Disabled	ec
Heapdumps on out of memory	Enabled	ec
Sysdumps	Enabled	ec
Where dump files are produced	Current directory	ec
Verbose output	Disabled	c
Boot classpath search	Disabled	c
JNI checks	Disabled	c
Remote debugging	Disabled	c
Strict conformance checks	Disabled	c
Quickstart	Disabled	c
Remote debug info server	Disabled	c
Reduced signaling	Disabled	c
Signal handler chaining	Enabled	c
Classpath	Not set	ec
Class data sharing	Disabled	c
Accessibility support	Enabled	e
JIT compiler	Enabled	ec
AOT compiler (AOT is not used by the JVM unless shared classes are also enabled)	Enabled	c
JIT debug options	Disabled	c
Java2D max size of fonts with algorithmic bold	14 point	e
Java2D use rendered bitmaps in scalable fonts	Enabled	e
Java2D freetype font rasterizing	Enabled	e
Java2D use AWT fonts	Disabled	e

JVM setting	AIX	IBM i	Linux	Windows	z/OS	Setting affected by
Default locale	None	None	None	N/A	None	e
Time to wait before starting plug-in	N/A	N/A	Zero	N/A	N/A	e
Temporary directory	/tmp	/tmp	/tmp	c:\temp	/tmp	e
Plug-in redirection	None	None	None	N/A	None	e
IM switching	Disabled	Disabled	Disabled	N/A	Disabled	e
IM modifiers	Disabled	Disabled	Disabled	N/A	Disabled	e
Thread model	N/A	N/A	N/A	N/A	Native	e
Initial stack size for Java™ Threads 32-bit. Use: -Xiss<size>	2 KB	2 KB	2 KB	2 KB	2 KB	c
Maximum stack size for Java Threads 32-bit. Use: -Xss<size>	256 KB	256 KB	256 KB	256 KB	256 KB	c
Stack size for OS Threads 32-bit. Use -Xmso<size>	256 KB	256 KB	256 KB	32 KB	256 KB	c
Initial stack size for Java Threads 64-bit. Use: -Xiss<size>	2 KB	N/A	2 KB	2 KB	2 KB	c
Maximum stack size for Java Threads 64-bit. Use: -Xss<size>	512 KB	N/A	512 KB	512 KB	512 KB	c
Stack size for OS Threads 64-bit. Use -Xmso<size>	256 KB	N/A	256 KB	256 KB	256 KB	c
Initial heap size. Use -Xms<size>	4 MB	4 MB	4 MB	4 MB	4 MB	c
Maximum Java heap size. Use -Xmx<size>	Half the available memory with a minimum of 16 MB and a maximum of 512 MB	2 GB	Half the available memory with a minimum of 16 MB and a maximum of 512 MB	Half the available memory with a minimum of 16 MB and a maximum of 512 MB See note.	Half the available memory with a minimum of 16 MB and a maximum of 512 MB	c
Compressed references	Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB	Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB	Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB	Disabled. From service refresh 4, enabled for -Xmx values of less than or equal to 25 GB	Disabled	ec
Page size for the Java object heap and code cache. For restrictions, see Configuring large page memory allocation	Operating system default	Operating system default	Architecture: Linux on x86 and AMD64/EM64T: 2 MB Linux on System z: 1 MB Other architectures: operating system default	Operating system default	1M pageable	c