ndmpcopy - question on levels 0-9

I'm preparing to copy several file systems to reduce the overall size after they have been deduped.  I've done some testing and ran a full copy level 0, then made some permission changes and created a new file, then ran a level 1.  The new files and permissions also copied over.  I then made additional changes and ran another level 1, again everything including permissions copied over.  I then added a few files, ran a level 4 and then a level 6, everything appears to be copying as expected.  After all these tests, I ran another level 1, which also copied over some change permissions and new files.

More than anything, I'm trying to determine the behavior of each level or why there are multiple levels since they all appear to do the same thing, minus level 0 for the initial sync.  I haven't been able to find anything documentation around the EMC supplied ndmpcopy tool, and there seems to be some variation among tools.

Anyone have an explanation on this?

Thanks in advance for any help.

Todd