JVM default values for -Xms (minimum heap size) and -Xmx (maximum heap size) if they are not set

Technote (FAQ)
Problem
This describes the Java™ virtual machine (JVM™) default values for -Xms (minimum heap size) and -Xmx (maximum heap size) if they are not set within WebSphere® Application Server. Note that if the initial and maximum heap values are set in WebSphere Application Server, it will override these default values.
Solution
When initial and maximum heap values are set in WebSphere Application Server, default values are overriden.

To determine if these values are set in WebSphere Application Server, use the administrative console to navigate to the appropriate tab for the JVM settings. If the "initial heap size" or "maximum heap size" fields are blank, the following default values will be used.

Default sizes for -Xmx (maximum heap size)
  • 1.2.2 and 1.3.0
    • Microsoft® Windows®: Half the real storage with a minimum of 16 M and a maximum of 2 G
    • AIX®, z/OS, Linux®, Solaris™: 64 M
  • 1.3.1
    • Windows: Half the real storage with a minimum of 16 M and a maximum of 2 G
    • AIX, and z/OS: 64 M
    • Linux: Half the real storage with a minimum of 16 M and a maximum of 512 M
    • Solaris: 64 M
    • HP-UX: 64 M
  • 1.4.1
    • Windows: Half the real storage with a minimum of 16 M and a maximum of 2 G
    • AIX, and z/OS: 64 M
    • Linux: Half the real storage with a minimum of 16 M and a maximum of 512 M
    • Solaris: 64 M
    • HP-UX: 64 M
  • 1.4.2
    • Windows: Half the real storage with a minimum of 16 M and a maximum of 2 G
    • AIX, and z/OS: 64 M
    • Linux: Half the real storage with a minimum of 16 M and a maximum of 512 M
    • Solaris: 64 M
    • HP-UX: 64 M

Default sizes for -Xms (minimum heap size)
  • 1.2.2 and 1.3.0
    • Windows: 4 M
    • AIX, z/OS, Linux, Solaris: 1 M
  • 1.3.1
    • Windows, AIX, Linux: 4 M
    • z/OS: 1 M
    • Solaris: 3584k
    • HP-UX: 2 M
  • 1.4.1
    • Windows, AIX, Linux: 4 M
    • z/OS: 1 M
    • Solaris: 1 M
    • HP-UX: 2 M
  • 1.4.2
    • Windows, AIX, Linux: 4 M
    • z/OS: 1 M
    • Solaris: 3670k
    • HP-UX: 2 M











Document Information

Product categories: Software, Application Servers, Distributed Application & Web Servers, WebSphere Application Server, Java SDK
Operating system(s): AIX, HPUX, Linux, Multi-Platform, OS/390, Solaris, Windows
Software version: 3.5, 4.0, 5.0, 5.1, 6.0
Software edition: Edition Independent
Reference #: 1132680
IBM Group: Software Group
Modified date: 2004-11-11