[xwiki-users] Offline storage migration / Export

Hi, I have an existing XWiki enterprise 1.3.1 running with a mysql backend and storage version 7351. I would like to upgrade to XWiki enterprise 2.6, but I am running into problems. - a xar export eats all ram, and the max heap is already the maximum of my 32-bit linux (-Xmx2600m) . When I increase it the jvm fails to start. The backup.xar stops at around 1.1GB, and then I gets OutOfMemory execeptions all over the place. - when I install 2.6 using the same mysql backend, the storage migration throws a massive amoutn of errors, mostly due to "Exception while saving object XWiki.XWikiUsers". This is migration R15428XWIKI2977. Is there a way to perform an offline migration, so I can debug where needed, ot a way to perform an export and import in a clean database offline? Regards, Leen