What does the option "-J-d64" of the jmap heap dump utility do?
<p>The man page says</p>

<blockquote>
  <p>If the given process is running on a 64-bit VM, you may need to specify the -J-d64 option</p>
</blockquote>

<p>and that's it. Some heap dump howtos do include it, without explanation.</p>

<p>More specifically, I'm trying to figure out if not specifying that option might be corrupting my heap dumps (jhat can't read them). Experimenting blindly is costly, as the heap is large, the system is a live one, and there are specific points during operation at which I need the dump.</p>
