Graph shown in memory tab, shows shows misleading information. may be a wrong graph.
How to produce this.
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1) start jconsole
2) connect to any java process (even to jconsole process it self).
3) keep the memory generation range to "ALL"
4) start obeerving jconsole memory graph (let it be heap).
5) disconnect for a 60seconds (with latest live connection button).
6) you will observe a break in the graph which is expected as it doesn;t know data between that time.
7) change and move on to any other memory areas (like eden space).
you will see a continues graph with no breaks.

I have seen this in solaris , windows-i586.
Here in this attached screen shots shows only for heap and edenspace memory allocations.

Please see the attachments, (16.50 and 16.51).