The two "man pages" [0] for the posix java launcher have this statement regarding Xmx:

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On Solaris 7 and Solaris 8 SPARC platforms, the upper limit for this value is approximately 4000m minus overhead amounts. On Solaris 2.6 and x86 platforms, the upper limit is approximately 2000m minus overhead amounts. On Linux platforms, the upper limit is approximately 2000m minus overhead amounts.
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The above statement is confusing and out-of-date for two reasons:

1. The limitations it describes only refer to 32-bit JVM implementations.
2. Both Solaris 7 and 8 have been EOL for ages now. Even Solaris 9 is EOL these days.

In response to the above two problems, I recommend either removing this sentence completely from these two pages, or making BOTH of these two changes:

- Add "When using the 32-bit HotSpot JVM, " to the beginning of the sentence.
- Remove all reference to Solaris 7 and 8 and simply say "on Solaris..."

Note that 8 has already removed this statement completely, so it may make sense to just follow that example for consistency.

[0]
  [ java - the Java application launcher (JDK 6) ]
  http://docs.oracle.com/javase/6/docs/technotes/tools/solaris/java.html

  [ java - the Java application launcher (JDK 7) ]
  http://docs.oracle.com/javase/7/docs/technotes/tools/solaris/java.html