Thanks Daniel. I have tried MWDumper and the results seem different from importDump.php i.e. the Formatting is messed up. In tracking down what I might be doing wrong - I would prefer to do this using the native method.
That sounds very *very* odd. because page content is imported as-is in both cases, it's not processed in any way. The only thing I can imagine is that things don't look right if you don't have all the templates imported yet.
Secondly, my question here is regarding PHP – not about the Database. I don’t see how a memory leak in PHP can be caused by the Database.
Just a warning on the side. Have a few hundred gigs handy.
But yes, the memory leak should be investigated. PHP is prone to this kind of thing, because it's not designed for long running processes, and not much tested for this kind of thing. Same goes for MediaWiki, i'm afraid.
-- daniel