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WebSphere Portal and the Microsoft Windows Boot.ini /3GB switch
 Technote (troubleshooting)
 
Problem(Abstract)
Can you use the Microsoft® Windows® Boot.ini /3GB switch with WebSphere® Portal?
 
Symptom
On Windows 32-bit, the maximum Java heap size a program can possibly get is around 1.50 - 1.75 GB, even if you have enabled the /3GB switch. With the /3GB switch, however, you can get more native heap memory.
 
Resolving the problem
The /3GB switch is not needed for most WebSphere Portal customers and environments.

If you do determine that you need to use the /3GB switch, review the following article about IBM Java and the Microsoft Windows Boot.ini /3GB switch:


This article and other resources can be found on the IBM® developerWorks > Java™ technology > IBM Developer kits > Diagnosis documentation page.


The following is an excerpt from the "Windows Java address space" article:
    Summary
    If you are having problems sharing a large Java heap with one or more of the following conditions:
    • I need lots of threads
    • I need lots of dynamic memory
    • I have a lot of java code and it takes a lot of JIT’d space

    then the /3GB switch is for you.

    To get extra space in your Java process:
    • Install a /3GB version of the Windows VM
    • Edit your BOOT.INI (then reboot, of course!)

    But note,
    1. We will support the /3GB switch only on platforms where Microsoft also supports it.
    2. The maximum Java heap size will not increase much when the /3GB switch is used.
    3. If you are inclined to try it out for yourself, albeit in an unsupported mode for Java, then you can use the EDITBIN tool as noted above.
    4. Watch out for 'gotchas' with "negative" pointers in your native code.
 
Related information
How to use the 4GT RAM Tuning feature
Available switch options for the Windows XP and the Win
Available switch options for the Windows 2000 Boot.ini
 
 
 

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Document information
 Product categories:
 Software
 Organizational Productivity, Portals & Collaboration
 Portals
 WebSphere Portal
 WebSphere Application Server Integration
 Operating system(s):
  Windows
 Software version:
  5.1, 6.0
 Reference #:
  1294917
 IBM Group:
 Software Group
 Modified date:
 2008-03-21

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